Protein chimaeras

Abstract

The present invention relates to protein chimaeras having novel trimer-to-monomer polypeptide junctions. Such chimaeras are useful, for example, for fusing together polypeptides from different viruses or tailocins. For example, a polypeptide monomer can be fused artificially to a native trimer displayed on a virus, such as phage. In this way monomers that are heterologous to the virus can be displayed. This opens up the possibility of producing novel display libraries where a repertoire of variant monomers are displayed on a common virus trimer structure, such as a tail fibre, spike or tailocin.

Description

PROTEIN CHIMAERAS TECHNICAL FIELD The present invention relates to protein chimaeras having novel trimer-to-monomer polypeptide junctions. Such chimaeras are useful, for example, for fusing together polypeptides from different viruses or tailocins. The invention relates also to monomer display libraries comprising carriers displaying such protein chimaeras. BACKGROUND Bacteriophages (phage) are viruses that infect bacteria. The infection of a bacterial cell begins when a phage virion adsorbs to the surface of the bacteria. For phages of Caudoviricetes, this process is mediated by receptor-binding proteins (RBPs) found at the distal end of the phage tail that binds to a cognate receptor available on the surface of the bacteria. Hence, the three-dimensional structure and the amino acid composition of these proteins affect both the affinity and the breadth of phage-host interactions thus, the host range of a given phage. Structurally, phage RBPs can be fibrous-long trimers in the form of tail fibres or short-stubby trimers, appearing like spikes, protruding from the baseplate of the phage virion (Nobrega et al.2018). On the bacterial surface, the available phage receptors can be diverse. These can be sugar moieties comprising residues of the core or repeating O- antigen units of lipopolysaccharide (LPS), capsular polysaccharides or cell wall, as well as proteinaceous structures such as the outer membrane porins, transporters, flagella or pili (Letarov and Kulikov, 2017). The pressure exerted by phage infections was hypothesised as one of the main underlying reason for diversification of surface phage receptors through mutations, recombinations (Koskella and Brockhurst, 2014) and as well the consequent genetic drift. Given the extreme diversity of these surface structures even within a single species of bacteria, phages must diversify and adapt their RBPs to increase chances of survival through maintaining a high breadth in infectivity. While evolutionarily this arms race can lead to selection of improved phages with novel RBP affinities, natural selection remains stochastic, cumbersome to execute and unpredictable to exploit phage virions for therapeutic purposes. Therefore, high-throughput methods are needed that allow diversification, selection, and testing of RBP-bacteria interactions with high speed and accuracy to enhance drug discovery and precision medicine technologies. Tailocins are bactericidal protein complexes produced by a wide variety of bacteria that kill closely related strains and may play a role in microbial community structure. Thanks to their high specificity, tailocins have been proposed as precision antibacterial agents for therapeutic applications.SUMMARY OF THE INVENTION The present invention relates to protein chimaeras having novel trimer-to-monomer polypeptide junctions. Such chimaeras are useful, for example, for fusing together polypeptides from different viruses. For example, a polypeptide monomer can be fused artificially to a native trimer displayed on a virus, such as phage. In this way monomers that are heterologous to the virus can be displayed. This opens up the possibility of producing novel display libraries where a repertoire of variant monomers are displayed on a common virus or tailocin with trimeric fibres or spikes. This enables the use of a universal virus with a common trimer feature that can be used to display different monomer variants. The resultant library can be readily screened to find monomers with desirable characteristics, such as ligand binding. To this end, the invention provides:- In a First Configuration A protein chimaera comprising (i) a polypeptide trimer comprising an interface; (ii) a polypeptide monomer; and (iii) a trimer-to-monomer adapter; wherein the adapter comprises a polypeptide, wherein the adapter polypeptide comprises an interface that is associated with the trimer interface, and wherein the adapter is associated with the protein monomer and the monomer is heterologous to the trimer wherein the chimaera is a non-naturally occurring protein chimaera. In a Second Configuration A tail fibre or spike of a transducing particle (eg, a virus or phage) or a tailocin, comprising the chimaera of any preceding claim, wherein the fibre or spike comprises (in N- to C-terminal direction) (i) said polypeptide trimer; (ii) said adapter; and (iii) said monomer; wherein the trimer is a trimer of a polypeptide that comprises (in N- to C-terminal direction) a first fragment and a second fragment, wherein the first fragment is heterologous to the second fragment and the second fragment comprises said trimer interface, wherein the first fragment is a first tail fibre or spike protein (or N-terminal fragment thereof). In a Third Configuration In a First Aspect:- A virus (eg, a phage) comprising the chimaera, tail fibre or spike of any Configuration.In a Second Aspect:- A library of tail fibres, spikes or tailocins, wherein each tail fibre, spike or tailocin is according to any Configuration, wherein the monomers of at least some of the members of the library differ from each other. In a Third Aspect:- A library comprising a plurality of adapter-monomers, wherein each adapter is an adapter as defined in any Configuration and associated (eg, covalently or electrostatically associated) with a polypeptide monomer, wherein each adapter-monomer comprises the adapter then the monomer in N- to C- terminal direction, wherein the monomers of at least some of the adapter-monomer members of the library differ from each other, optionally wherein each adapter comprises an N-terminal interface that is associated with a polypeptide trimer interface. In a Fourth Configuration A library comprising a plurality of polypeptide monomers, wherein the monomers differ from each other (optionally wherein the monomers are variants of a parental monomer and differ from each other by one or more amino acid residues), wherein each said monomer is fused to a protein displayed by a carrier (eg, a virus (such as a phage), cell or nanoparticle). In an aspect, C-terminal peptide loops of monomers of at least some of the members of the library differ from each other. In a Fifth Configuration In a First Aspect:- A method of selecting a tail fibre or spike sequence, the method comprising contacting a library as described herein with a ligand, wherein the tail fibres are displayed on carriers, wherein each carrier comprises a respective nucleic acid encoding the tail fibre or spike that it displays, wherein monomers of tail fibres or spikes of the library bind to the ligand, the method comprising isolating nucleic acid of a carrier whose chimeric fibre or spike bound to the ligand; and determining the nucleotide sequence of the monomer of said fibre or spike and / or isolating said fibre or spike. In a Second Aspect:- A method of producing a tail fibre or spike, the method comprising (i) providing a protein expression construct, wherein the construct comprises a nucleic acid that encodes a phage tail fibre or spike, the nucleic acid comprising said nucleotide sequence determined by the method of the First Aspect; (ii) expressing the tail fibre or spike encoded by the construct; andoptionally isolating the tail fibre or spike. In a Sixth Configuration In a First Aspect:- A method of producing a tail fibre or spike, the method comprising (i) contacting a library as described herein with a ligand, wherein the monomers are displayed on carriers, wherein each carrier comprises a respective nucleic acid encoding the monomer that it displays, wherein monomers of the library bind to the ligand; (ii) isolating nucleic acid of a carrier whose monomer bound to the ligand; and (iii) determining the nucleotide sequence of the monomer of step (ii); the method further comprising (iv) providing a protein expression construct, wherein the construct comprises a nucleic acid that encodes a phage tail fibre or spike, the nucleic acid comprising said nucleotide sequence determined in step (iii) or a nucleotide sequence that differs by no more than 5 codon changes; (v) expressing tail fibre or spike encoded by the construct; and optionally isolating tail fibre or spike. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1: (A) Genomic and structural composition of T4- and T2 / T6-like fibres. Product of gp57a is a chaperone needed for correct folding of both gp34 and gp37. Gp38 serves as a chaperone in T4-like fibres and as the actual receptor binding protein in T2 / T6-like fibres capping gp37 distal C-terminus (dashed box). (B) Architectural composition of gp37-gp38 (dashed in A) in T2 / T6-like fibres (modified from Dunne et al., 2018). (C) Genomic and structural composition of P2 fibre. Product of gene G serves as a chaperone for correct folding of P2 fibre H analogous to gp38 of T4. Figure 2: Genomic design of chimeric fibre under the arabinose promoter and pairwise alignment of amino acid residues of P2 H459-516(SEQ ID NO: 195) and a184 gp37884-943(SEQ ID NO: 196) (box). Ribosomal binding sites (RBS) are indicated. Grey boxes indicate the N- and C-terminals of chimeric P2 fibre, respectively. Black arrow indicates the translational fusion point in the construct. Figure 3: Plasmid p1267. Coding regions and corresponding genes are indicated with light arrows. P, promoter; RBS, ribosomal binding site; P4 Pac site, packaging signal for P4. Figure 4: (A) Efficiency of plating of Tevenvirinae subfamily member a184. Ten-fold dilutions of the a184 lysates in SM buffer were spotted on lawns of wild-type b52 and the Tsx knockout mutant ofb52 (b3364). Lack of plaque formation on b3364 demonstrates that a184 gp38 is dependent on presence of Tsx for adsorbing to bacterial cells. (B) Transduction assays performed with native and chimeric P2 / P4 particles demonstrating that successful delivery of GFP+ DNA cargo with native fibre requires an intact LPS whereas the chimeric fibre requires presence of Tsx, as its adsorption to the cells is mediated by gp38 from a184. DETAILED DESCRIPTION In complex and larger wild-type myoviruses in the Tevenvirinae subfamily Tequatrovirus genus, RBPs that mediate receptor binding comprise six, digited long tail fibres each comprised of proteins gp34, gp35, gp36 and gp37, respectively extending from baseplate to periphery (C-terminus of the tail fibre) with a stoichiometry of 3:1:3:3 (Leiman et al., 2010) (Figure 1A). Additionally, trimerization of gp34 and gp37 requires the activity of chaperone gp57a (Hashemolhosseini et al.1998). Although formation of functional fibres also requires an additional gene gp38, the activity of gp38 differs in different fibres. In fibres of T4-like phages, gp38 is a chaperone that correctly folds the gp37 monomers into a trimer and is not found in the mature fibre. Thus, in this case the gp37 trimer is the RBP that mediates the binding to the receptor (Bartual et al., 2010). In T2 / T6-like fibres however, the C-terminus of gp37 comprises an intramolecular chaperone (Peptidase_S74 [PF13884]) that trimerizes the gp37 monomers and gets cleaved off, forming the interface at the distal end of gp37 trimer that is capped by a single monomer of gp38 (Figure 1A / B, Dunne et al., 2018). As a result, the gp38 is the actual RBP in the T2 / T6-like phages. RBP gp38 is comprised of a conserved N-terminal domain (adapter) that caps the folded gp37 trimer, and a C-terminal domain responsible for binding to the cognate receptor both of which are linked by a linker amino acid sequence (Figure 1B). The amino acid sequences of C-terminal domain of RBP gp38s display unique features, namely several stretches of highly conserved glycine residues flanked by stretches of variable residues. Accumulating evidence over several decades identified these stretches of variable residues as the “hot spots” for spontaneous mutations that enable phages to bind novel receptors (Morona and Henning, 1984; Riede et al., 1987; Montag et al., 1987; Drexler et al., 1989; Tetart et al., 1998; Morita et al., 2002; Yoichi et al., 2005; Trojet et al., 2011). It became clear recently with the resolved structure of gp38 (Dunne et al., 2018) that while glycine stretches fold into a stable sandwich-like architecture, the variable stretches bend out forming loops at the distal end of the phage fibre. As a result, natural RBP gp38 represents an ingenious evolutionary advantage for this group of phages that allows diversification of the binding affinity through mutational and recombinational alteration of the variable stretches, without compromising the gp38 architecture. Despite its elegant structure, the in vitro designing and engineering of RBP binding affinity has been limited with necessity of back engineering the mutations to phage backbone via homologous recombination and selection of recombinants thereof, all together hampers the speed and accuracy needed for discovery of novel binding affinities (Morita et al., 2002; Trojet et al.2011).We engineered this binding module on a simple myovirus coliphage P2 / P4 and created a platform with a novel fibre arrangement that displays a gp38 protein (which is not normally found on P2 / P4 fibres), DNA sequence of which is packed into virion heads. By rational design and engineering we found that we could create a chimaeric fibre having an N-terminal trimer portion that interfaced with a monomer portion (gp38) to create synthetic functional fibres with new RBP functionality. We surprisingly found that these synthetic virions could only bind and deliver the DNA cargo to bacterial cells that carry a suitable cognate receptor of the displayed gp38. In simple myoviruses, such as members of Peduovirinae subfamily (eg, Escherichia virus P2 / P4, Pseudomonas virus phiCTX), members of Muvirus genus (eg, Escherichia virus Mu), Punavirus genus (eg, Escherichia virus P1) or phage tail-like bacteriocins (tailocins) with similar structural forms (eg, R-type pyocins), RBPs are formed as a non-digited trimeric fibre from a single gene with the chaperone activity supplied from a flanking downstream gene (Haggard-Ljungquist et al.1992; Williams et al., 2008; Ghequire and De Mot, 2015; North et al., 2019). In Escherichia virus P2 / P4, six trimeric fibres, N-terminals of which are associated with the baseplate of the tail are formed from gene H while the downstream flanking gene G is needed for virions with functional fibres (Figure 1C). Here, G serves as a chaperone and thus not surprisingly shares a common domain (Caudo_TAP [PF02413]) with other tail fibre assembly proteins found in other similar phages, such as Mu (North et al., 2019), and distant phages such as lambda (gpK) or T4 (gp38). We advantageously found that we could translationally fuse P2 H N-terminal with a184 gp37 C-terminal and successfully co-express the cognate gp38 and gp57a (Figure 2). Virus a184 phage is a member of Tevenvirinae subfamily Tequatrovirus genus with T2 / T6-like fibre. Using this arrangement, we could create P2 / P4 virions that do not only display gp38 monomer, but also opening the useful possibility that we can display other monomeric proteins of interest (eg, an antibody single variable domain) on the tip of an otherwise trimeric fibre. Hence, the novel platform allows both repertoire display of gp38 variant libraries and the selection of new binding affinities via delivery of a DNA cargo into bacteria of interest. This advantageously enables interrogation of vast repertoire display libraries coupled with simple screening for desired RBPs. Thus, more extensive choice and quicker generation of synthetic virus RBPs can be achieved than prior art methods. The invention thus provides:- A protein chimaera comprising (i) a polypeptide trimer comprising an interface; (ii) a polypeptide monomer; and (iii) a trimer-to-monomer adapter; wherein the adapter comprises a polypeptide, wherein the adapter polypeptide comprises an interface that is associated with the trimer interface, and wherein the adapter is associated with the proteinmonomer and the monomer is heterologous to the trimer wherein the chimaera is a non-naturally occurring protein chimaera. In an embodiment, the adapter comprises only one said polypeptide. In another embodiment, the adapter comprises a plurality of said polypeptides which together form the interface. The adapter may be covalently bonded to the monomer (optionally via a peptide linker). By “heterologous to the trimer” it is intended that the monomer and the chimaeric trimer do not naturally occur together, ie, they are a synthetic combination. Optionally, (i) said interfaces are hydrophobically associated together; and / or (ii) the adapter interface comprises one or more charged amino acids, the trimer interface comprises one or more charged amino acids, and said amino acid(s) of the adapter interface are electrostatically associated with said amino acid(s) of the trimer. Each interface may have a surface area of at least 800 Å2. Optionally each said surface area is from 800-1200, 800-1100, 800-1000, or 900-950 Å2. Oppositely charged amino acids are associated together to provide said electrostatic association. The hydrophobic amino acids are gly, ala, val, leu, ile, met, pro, phe, tyr, trp. These amino acids have hydrocarbon sidechains that, because of their non-polar chemistry, are forced into close association (hydrophobic "bonds") in an aqueous solvent. In an embodiment, the chimaera is in an aqueous medium. The interfaces can be hydrophobic wherein the adapter interface comprises one or more hydrophobic amino acids, the trimer interface comprises one or more hydrophobic amino acids, and said hydrophobic amino acid(s) of the adapter interface are hydrophobically associated with said hydrophobic amino acid(s) of the trimer. Any monomer herein may be a phage gp38 protein (for example, a wild-type or modified gp38 protein, eg, a mutated gp38 protein). Any monomer herein may be an antibody single variable domain. Any monomer herein may be a non-Ig single variable domain that is capable of binding to an antigen, eg, a fibronectin, avimer, affibody or DARPin domain). Optionally, (i) the adapter is heterologous to the trimer; and / or(ii) the adapter is heterologous to the monomer. Optionally, the trimer comprises an amino acid sequence that is naturally found in a first phage or tailocin tail fibre or spike and the adapter or monomer comprises an amino acid sequence that is not found in said tailocin or first phage tail fibre or spike. The protein chimaera may be comprised by a transduction particle (optionally a phage), optionally wherein the particle comprises capsid proteins of a Caudoviricetes phage or a myovirus (eg, a myovirus of the Tevenvirinae subfamily, optionally of the Tequatrovirus genus). The protein chimaera may be comprised by a transduction particle (optionally a phage), wherein the particle comprises capsid proteins of a myovirus of the Peduovirinae subfamily (eg, Escherichia virus P2 / P4, Pseudomonas virus phiCTX). The protein chimaera may be comprised by a transduction particle (optionally a phage), wherein the particle comprises capsid proteins of a Muvirus genus (eg, Escherichia virus Mu) and / or Punavirus genus (eg, Escherichia virus P1). The protein chimaera may be comprised by a transduction particle (optionally a phage), wherein the particle comprises capsid proteins of a Caudoviricetes phage and (i) the monomer is heterologous to said phage; and / or (ii) the particle comprises DNA packaged by said capsid proteins, wherein the DNA is heterologous to said phage. Optionally, the DNA encodes a non-phage protein or RNA, optionally a CRISPR guide RNA or crRNA. The DNA may comprise a packaging site (eg, a pac or cos site) of said phage. The protein chimaera may be comprised by a transduction particle (optionally a phage) that is capable of infecting a target bacterial or archaeal cell, optionally wherein the particle comprises DNA that encodes (i) an agent that is toxic to the cell; or (ii) a bacterial, archaeal, animal (eg, human, eg, a cytokine or antibody fragment), plant or yeast protein. Optionally, (a) the monomer comprises a polypeptide of a T-even phage tail fibre (eg, a gp38 polypeptide or fragment thereof such as a C-terminal fragment of a gp38, eg, comprising an adhesin tip of a phage or tailocin tail fibre); (b) the trimer is heterologous to T-even phages; (c) the monomer comprises a polypeptide of a T2 or T6 phage (eg, a gp38 polypeptide orfragment thereof; or a gp38 variant polypeptide) and the trimer is heterologous to said phage; and / or (d) the adapter is an adapter comprised by a tail fibre of a T-even phage (eg, a T2 or T6 phage) and the monomer is a gp38 polypeptide of said phage or a variant of such a gp38 polypeptide, wherein the T-even phage tail fibre comprises in N- to C-terminal direction a gp37 trimer, said adapter and said gp38 monomer. Optionally, the agent is a crRNA and / or a Cas. The variant is capable of binding to a cognate ligand, such as a bacterial surface receptor. In an embodiment, the trimer is heterologous to said T-even phage tail fibre. The trimer may comprise a polypeptide fragment of a polypeptide trimer of a virus (eg, phage) or tailocin tail fibre or spike. The trimer may be associated with a tail fibre base plate polypeptide (eg, a P2 base plate polypeptide). For example, the chimaera is comprised by a tail fibre of a phage and the trimer of the chimaera is associated with a baseplate of the phage. For example, the phage is a T-even, T-odd, P2 or lambda phage. In an embodiment, the chimaera is comprised by (i) a phage tail fibre and the tail fibre comprises (in basal to apical N- to C-terminal direction) said trimer, said adapter and said monomer, wherein the trimer is a trimer of a polypeptide that comprises (in N- to C-terminal direction) a first fragment and a second fragment, wherein the first fragment is heterologous to the second fragment and the second fragment comprises said trimer interface; (ii) a phage spike and the spike comprises (in N- to C-terminal direction) said trimer, said adapter and said monomer, wherein the trimer is a trimer of a polypeptide that comprises (in N- to C-terminal direction) a first fragment and a second fragment, wherein the first fragment is heterologous to the second fragment and the second fragment comprises said trimer interface; (iii) a tailocin fibre and the tailocin fibre comprises (in N- to C-terminal direction) said trimer, said adapter and said monomer, wherein the trimer is a trimer of a polypeptide that comprises (in N- to C-terminal direction) a first fragment and a second fragment, wherein the first fragment is heterologous to the second fragment and the second fragment comprises said trimer interface; or (iv) a tailocin spike and the spike comprises (in N- to C-terminal direction) said trimer, said adapter and said monomer, wherein the trimer is a trimer of a polypeptide that comprises (in N- to C-terminal direction) a first fragment and a second fragment, wherein the first fragment is heterologous to the second fragment and the second fragment comprises said trimerinterface. In embodiments, the trimer interface faces away from the fibre base. In embodiments, the trimer interface faces away from the N-terminus of the chimaera. When the tail fibre or spike is attached to a phage or tailocin, the proximal to distal direction of the fibre or spike is equivalent to N- to C-terminal direction herein. Heterologous fragments are not naturally found in the same phage or the same tailocin. The combination of the fragments is non-naturally occurring. Optionally the first fragment comprises a base plate polypeptide or fragment thereof. Optionally the first fragment comprises at least 50, 60, 70, 80 or 90% of the N-terminal part of a phage fibre. Optionally the first fragment comprises at least 50, 60, 70, 80 or 90% of the N-terminal part of a tailocin fibre. Optionally, the first fragment may be a fragment of a tail fibre polypeptide of a first virus, and the second fragment is a fragment of a tail fibre polypeptide of a second virus. Optionally, the first fragment may be a fragment of a spike polypeptide of a first virus, and the second fragment is a fragment of a spike fibre polypeptide of a second virus. Optionally, the first fragment may be a fragment of a fibre or spike polypeptide of a tailocin, and the second fragment is a fragment of a fibre polypeptide of a virus. Optionally, the first fragment may be a fragment of a fibre or spike polypeptide of a first tailocin, and the second fragment is a fragment of a fibre polypeptide of a second tailocin. Each virus may be a phage. The first fragment may be a fragment of a tail fibre of a virus (eg, a phage) that is associated with a tail fibre base plate polypeptide (eg, a P2 base plate polypeptide) of the virus. The first fragment may be a fragment of a tail fibre of a tailocin that is associated with a tail fibre base plate polypeptide (eg, a P2 base plate polypeptide) of the tailocin. The first fragment may be a fragment of a phage or tailocin tail fibre or spike. Alternatively, the first fragment may be a synthetic polypeptide that is not naturally found in a phage, or not naturally found in a phage that also comprises the first fragment. Additionally or alternatively, the first fragment may be a synthetic polypeptide that is not naturally found in a tailocin, or not naturally found in a tailocin that also comprises the first fragment.Optionally, (i) the first fragment is heterologous to the adapter; (ii) the first fragment is heterologous to the monomer; (iii) the first fragment is heterologous to the adapter and the monomer; (iv) the first fragment is a fragment of a polypeptide of a tail fibre of a first phage, and the adapter is comprised by a tail fibre or spike of a second phage, wherein the first and second phage are different types of phage (preferably, in this embodiment the adapter is comprised by a tail fibre of the second phage).; (v) the first fragment is a fragment of a polypeptide of a spike of a first phage, and the adapter is comprised by a tail fibre or spike of a second phage, wherein the first and second phage are different types of phage (preferably, in this embodiment the adapter is comprised by a spike of the second phage); (vi) the first fragment is a fragment of a polypeptide of a tail fibre of a first tailocin, and the adapter is comprised by a tail fibre or spike of a second tailocin, wherein the first and second tailocins are different types of tailocin (preferably, in this embodiment the adapter is comprised by a tail fibre of the second tailocin); (v) the first fragment is a fragment of a polypeptide of a spike of a first tailocin, and the adapter is comprised by a tail fibre or spike of a second tailocin, wherein the first and second tailocins are different types of tailocin (preferably, in this embodiment the adapter is comprised by a spike of the second tailocin); (vi) the first fragment is a fragment of a polypeptide of a tail fibre of a phage, and the adapter is comprised by a tail fibre or spike of a tailocin (preferably, in this embodiment the adapter is comprised by a tail fibre of a tailocin); (vii) the first fragment is a fragment of a polypeptide of a spike of a phage, and the adapter is comprised by a tail fibre or spike of a tailocin (preferably, in this embodiment the adapter is comprised by a spike of a tailocin); (viii) the first fragment is a fragment of a polypeptide of a tail fibre of a tailocin, and the adapter is comprised by a tail fibre or spike of a phage (preferably, in this embodiment the adapter is comprised by a tail fibre of a phage); (ix) the first fragment is a fragment of a polypeptide of a spike of a tailocin, and the adapter is comprised by a tail fibre or spike of a phage (preferably, in this embodiment the adapter is comprised by a spike of a phage).For example, the phages have different host ranges. For example, the phages are different species of phage. For example, the phages are members of different genera, families, subfamilies or orders of phage. Preferably, the phages are tailed phages. Preferably, the phages are Caudoviricetes phages. In an embodiment, the first phage is a P2 phage. In an embodiment, the second phage is a T-even phage. In an embodiment, the first phage is not a T2 phage. In an embodiment, the first phage is not a T6 phage. In an embodiment, the first phage is a P2 phage and the second phage is a T-even phage (eg, a T2 or T6 phage). In an embodiment, the first phage is a P2 phage and the second phage is a T2 phage. n an embodiment, the first phage is a P2 phage and the second phage is a T6 phage. n an embodiment, the first phage is a P2 phage and the second phage is a T4 phage. In an embodiment, the first phage is a P2 phage and the second phage is a T-odd phage. Optionally, the second phage is selected from Caudoviricetes, myovirus (eg, a myovirus of the Tevenvirinae subfamily, optionally of the Tequatrovirus genus or myovirus of the Peduovirinae subfamily (eg, Escherichia virus P2 / P4, Pseudomonas virus phiCTX)), Muvirus (eg, Escherichia virus Mu) and Punavirus genus (eg, Escherichia virus P1) phage. The “heterologous” components do not naturally occur together, eg, in the same wild-type phage or virus. Optionally, (i) the second fragment comprises a gp37 trimer-to-monomer interface and the adapter is linked to a gp38 monomer and the adapter comprises a monomer-to-trimer interface that is associated with the gp37 trimer-to-monomer interface; (ii) the second fragment comprises a gp5 trimer-to-monomer interface and the adapter comprises a gp5.4 monomer-to-trimer interface that is associated with the gp5 trimer-to- monomer interface; (iii) the second fragment comprises a bacterial type VI secretion system VgrG protein trimer- to-monomer interface and the adapter comprises a cognate bacterial type VI secretion system PAAR-repeat protein monomer-to-trimer interface that is associated with the VgrG protein trimer-to-monomer interface. The tail fibre, spike or protein may comprise in N- to C-terminal direction (i) said first fragment (which is a N-terminal fragment of a tail fibre trimer of a first phage), (ii) said second fragment (which is a C-terminal fragment of a tail fibre trimer of a second phage, wherein the second phage does not comprise said first fragment), wherein the second fragment comprises a gp37 trimer-to- monomer interface, (iii) the adapter and (iv) a gp38 monomer, wherein the adapter is linked to themonomer and the adapter comprises a monomer-to-trimer interface that is associated with the gp37 interface. Optionally, the gp37 and / or gp38 is a T2-like (eg, a T2) gp37 and gp38. Optionally, the gp37 and / or gp38 is a T6-like (eg, a T6) gp37 and gp38. Optionally, the gp37 is a gp37 comprising a C-terminal peptidase_S74 (PF13884) domain (and in an example the gp38 is a cognate gp38). Optionally, (i) the gp37 and / or gp38 is a Salmonella phage S16 gp37 and gp38 respectively; or (ii) the gp5 and / or gp5.4 is a T-even (eg, T2 or T6) phage gp5 and gp5.4 respectively. Optionally, (i) the trimer interface is a trimer-to-monomer interface of a trimer of a phage or tailocin tail fibre or spike and the adapter interface is a cognate monomer-to-trimer interface of a monomer of said tail fibre or spike; or (ii) the trimer interface is a trimer-to-monomer interface of a trimer of a bacterial type VI secretion system and the adapter interface is a cognate monomer-to-trimer interface of a monomer of said bacterial type VI secretion system, eg, wherein the monomer is comprised by a PAAR-repeat protein. The adapter polypeptide may be fused to the monomer, optionally via a peptide linker. The chimaera may be comprised by a transduction particle (eg, phage) tail fibre or spike and the monomer is at the C-terminus of the said tail fibre or spike. The chimaera may be comprised by a tailocin (eg, R-type pyocin) tail fibre or spike and the monomer is at the C-terminus of the said tail fibre or spike. In an embodiment, the trimer is a polypeptide homotrimer. The adapter may comprise an alpha-helix polypeptide bundle and the bundle comprises the adapter interface. The adapter may comprise a T-even (eg, T2 or T6) phage tail fibre polypeptide or fragment thereof, optionally linked to a monomer comprising a gp38 polypeptide or a fragment thereof. Optionally, the polypeptide or fragment comprises an alpha helix polypeptide bundle, wherein the bundle comprises (i) an interface that associates with the trimer and (ii) an attachment point for the monomer or a peptide linker that links the attachment point to the monomer. Examples of suitable linkers are disclosed herein, eg, G4Sn linkers, where n=an integer, such as 1, 2, 3, 4, 5 or 6. A suitablelinker is FIGRSKEE or MIGRSVEI. Optionally, the linker is a flexible linker. Optionally, the linker is a rigid linker. The skilled addressee will know examples of these. The monomer may comprises a beta helix and / or a PG II sandwich domain. The monomer may comprises a ligand binding site, optionally at the C-terminus of the chimaeric protein. In an embodiment, the N-terminus of the trimer is associated with a base plate of a phage or tailocin. The invention provides:- A tail fibre or spike of a transduction particle (eg, a virus or phage) or a tailocin, the fibre or spike comprising a chimaera described herein, wherein the chimaera of the fibre or spike comprises (in N- to C-terminal direction) (i) said polypeptide trimer; (ii) said adapter; and (iii) said monomer; wherein the trimer is a trimer of a polypeptide that comprises (in N- to C-terminal direction) a first fragment and a second fragment, wherein the first fragment is heterologous to the second fragment and the second fragment comprises said trimer interface, wherein the first fragment is a first tail fibre or spike protein (or N-terminal fragment thereof). In a preferred embodiment, the fragments are joined directly together at a junction. Optionally, the chimaera comprises immediately N-terminal to the junction an amino acid sequence selected from SEQ ID NOs: 24-41; or an amino acid sequence that is at least 70, 80, 85, 90 or 95% identical to said selected sequence. Optionally, the chimaera comprises immediately C-terminal to the junction an amino acid sequence selected from SEQ ID NOs: 42-59; or an amino acid sequence that is at least 70, 80, 85, 90 or 95% identical to said selected sequence. Optionally, any chimaera herein comprises an amino acid sequence selected from SEQ ID NOs: 60-77 and 192; or an amino acid sequence that is at least 70, 80, 85, 90 or 95% identical to said selected sequence. In an embodiment, the chimaera comprises SEQ ID NO: 192 or an amino acid sequence that is at least 70, 80, 85, 90 or 95% identical to SEQ ID NO: 192. Optionally, a gp38 herein comprises SEQ ID NO: 194 or an amino acid sequence that is at least 70, 80, 85, 90 or 95% identical to SEQ ID NO: 194.Optionally an adapter herein comprises an amino acid sequence selected from SEQ ID NOs: 79-85, eg, SEQ ID NO: 79; or a sequence that is at least 70, 80, 90 or 95% identical to said selected sequence. Optionally an adapter herein comprises a motif sequence selected from SEQ ID NOs: 157-163. For example, the adapter comprises at least 2 or 3 of said sequences. For example, the adapter comprises (in N-to C-terminal direction) SEQ ID NOs: 157 and 159-161. Optionally a monomer herein comprises an amino acid sequence selected from SEQ ID NOs: 143- 149, eg SEQ ID NO: 143; or a sequence that is at least 70, 80, 90 or 95% identical to said selected sequence. Optionally a linker herein comprises an amino acid sequence selected from SEQ ID NOs: 86-142, eg, SEQ ID NO: 99; or a sequence that is at least 70, 80, 90 or 95% identical to said selected sequence. Optionally an adapter, linker and monomer sequence (in N- to C-terminal direction) is selected from SEQ ID NOs: 150-156, eg, SEQ ID NO: 150; or a sequence that is at least 70, 80, 90 or 95% identical to said selected sequence. The first and second fragments are optionally respectively fragments of first and second tail fibre proteins (or fragments thereof) of different phage (or from a tailocin and a phage), optionally wherein the first fragment is from a Peduovirinae, Muvirus (optionally P2), Punavirus (optionally P1) or tailocin (optionally R-type pyocin) and the second fragment is from a Tevenvirinae (optionally a T2 or T6) phage. The first fragment may be a first tail fibre or spike protein (or N-terminal fragment thereof) that is directly attached to the base plate of a phage or tailocin. The first protein may be a phage P2 protein H or homologue thereof of a different phage or a tailocin. The first protein is in an embodiment a phage P2 protein H. The first protein may be filamentous phage protein, or fused to a protein of a filamentous phage, eg, a M13 pIII protein. The first protein may be a Caudoviricetes or Inovirus (can use Tubulovirales to include more options fx) phage protein. The first fragment optionally comprises at least the N-terminal-most 100, 150, 200, 250, 300, 350 or 400 (eg, 379) consecutive amino acids of the first protein. The first fragment optionally comprises no less than the N-terminal-most 100 and no more than the N-terminal-most more 150, 200, 250, 300, 350 or 400 (eg, 379) consecutive amino acids of the first protein. The second fragment is optionally a fragment of a second tail fibre or spike protein (or C-terminal fragment thereof) and the fragments are joined directly together at a junction; and wherein the amino acid sequence of the first fragment joined to the second fragment comprises a window (W1) of alength (L1) of at least 15 consecutive amino acids, wherein the window comprises the junction and is (i) at least 50% similar or identical to a window (W2) of consecutive amino acids of the first tail fibre or spike protein wherein W2 is an amino acid sequence of length L1; and (ii) at least 50% similar or identical to a window (W3) of consecutive amino acids of the second tail fibre or spike protein wherein W3 is an amino acid sequence of length L1. L1 is, for example, at least 16, 17, 18, 19, 20, 25 or 30 consecutive amino acids. W1 is, for example at least 50, 60, 70, 80, 90 or 95 % similar or identical to a window (W2) of consecutive amino acids of the first tail fibre or spike protein wherein W2 is an amino acid sequence of length L1. W1 is, for example at least 50, 60, 70, 80, 90 or 95 % identical to a window (W2) of consecutive amino acids of the first tail fibre or spike protein wherein W2 is an amino acid sequence of length L1. W1 is, for example at least 50, 60, 70, 80, 90 or 95 % similar to a window (W2) of consecutive amino acids of the first tail fibre or spike protein wherein W2 is an amino acid sequence of length L1. W1 is, for example at least 50, 60, 70, 80, 90 or 95 % similar or identical to a window (W3) of consecutive amino acids of the second tail fibre or spike protein wherein W3 is an amino acid sequence of length L1. W1 is, for example at least 50, 60, 70, 80, 90 or 95 % identical to a window (W3) of consecutive amino acids of the second tail fibre or spike protein wherein W3 is an amino acid sequence of length L1. W1 is, for example at least 50, 60, 70, 80, 90 or 95 % similar to a window (W3) of consecutive amino acids of the second tail fibre or spike protein wherein W3 is an amino acid sequence of length L1. Optionally, (a) the protein chimaera comprises a window (W4) of X consecutive amino acids immediately N-terminal of the junction; (b) the protein chimaera comprises a window (W5) of Y consecutive amino acids immediately C-terminal of the junction; (d) X is at least 4; (e) Y is at least 4; and (f) (i) the amino acid sequence of W4 is at least 50% identical or similar to the C-terminal- most sequence of X consecutive amino acids of the first fragment; and / or (ii) the amino acid sequence of W5 is at least 50% identical or similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment. For example, X is at least 4, 5, 6, 7 or 8. Additionally or alternatively, for example, Y is at least 4, 5, 6, 7 or 8. In (f)(i), for example the amino acid sequence of W4 is at least 50, 60, 70, 80, 90 or 95% identical or similar to the C-terminal-most sequence of X consecutive amino acids of the firstfragment. In (f)(i), for example the amino acid sequence of W4 is at least 50, 60, 70, 80, 90 or 95% identical to the C-terminal-most sequence of X consecutive amino acids of the first fragment. In (f)(i), for example the amino acid sequence of W4 is at least 50, 60, 70, 80, 90 or 95% similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment. In (f)(ii), for example the amino acid sequence of W5 is at least 50, 60, 70, 80, 90 or 95% identical or similar to the N- terminal-most sequence of X consecutive amino acids of the second fragment. In (f)(ii), for example the amino acid sequence of W5 is at least 50, 60, 70, 80, 90 or 95% identical to the N-terminal-most sequence of X consecutive amino acids of the second fragment. In (f)(ii), for example the amino acid sequence of W5 is at least 50, 60, 70, 80, 90 or 95% similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment. The chimaera may comprise amino acid sequence GDNDTG (SEQ ID NO: 20) immediately N- terminal to the junction; or LVHGGD (SEQ ID NO: 197) immediately C-terminal to the junction. Optionally, the junction is comprised by amino acid sequence GDNDTGLVHGGD (SEQ ID NO: 198), DNDTGLVHGG (SEQ ID NO: 199), NDTGLVHG (SEQ ID NO: 200), DTGLVH (SEQ ID NO: 201) or TGLV (SEQ ID NO: 202). The junction may be between G and L in any of these sequences. Amino acid sequences are in 5’ to 3’ direction. Optionally, A: (i) the amino acid sequence of W4 is at least 50% identical or similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment; and (ii) the amino acid sequence of W5 is at least 40% identical or similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment; or B: (ii) the amino acid sequence of W4 is at least 40% identical or similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment; and (ii) the amino acid sequence of W5 is at least 50% identical or similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment. For example, in A, the amino acid sequence of W4 is at least 50, 60, 70, 80, 90 or 95% identical or similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment. For example, in A, the amino acid sequence of W4 is at least 50, 60, 70, 80, 90 or 95% identical to the C- terminal-most sequence of X consecutive amino acids of the first fragment. For example, in A, the amino acid sequence of W4 is at least 50, 60, 70, 80, 90 or 95% similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment. For example, in A, the amino acid sequence of W5 is at least 40, 50, 60, 70, 80, 90 or 95% identical or similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment. For example, in A, the amino acidsequence of W5 is at least 40, 50, 60, 70, 80, 90 or 95% identical to the N-terminal-most sequence of X consecutive amino acids of the second fragment. For example, in A, the amino acid sequence of W5 is at least 40, 50, 60, 70, 80, 90 or 95% similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment. For example, in B, the amino acid sequence of W4 is at least 40, 50, 60, 70, 80, 90 or 95% identical or similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment. For example, in B, the amino acid sequence of W4 is at least 40, 50, 60, 70, 80, 90 or 95% identical to the C-terminal-most sequence of X consecutive amino acids of the first fragment. For example, in B, the amino acid sequence of W4 is at least 40, 50, 60, 70, 80, 90 or 95% similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment. For example, in B, the amino acid sequence of W5 is at least 50, 60, 70, 80, 90 or 95% identical or similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment. For example, in B, the amino acid sequence of W5 is at least 50, 60, 70, 80, 90 or 95% identical to the N-terminal-most sequence of X consecutive amino acids of the second fragment. For example, in B, the amino acid sequence of W5 is at least 50, 60, 70, 80, 90 or 95% similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment. Optionally in the tail fibre or spike A: the first fragment is a N-terminal fragment of a tail fibre of a phage that is not a T-even phage; and B: the adapter comprises a polypeptide (or fragment thereof) of a T-even phage and / or the monomer comprises a polypeptide (or fragment thereof) of a T-even phage. Optionally in the tail fibre or spike A: the first fragment is a N-terminal fragment of a tail fibre of a phage that is not a T-even phage; and B: the trimer comprises a polypeptide (or fragment thereof, optionally the second fragment) of a T-even phage. Optionally in the tail fibre or spike A: the first fragment is a N-terminal fragment of a tail fibre of a tailocin; and B: the adapter comprises a polypeptide (or fragment thereof) of a T-even phage and / or the monomer comprises a polypeptide (or fragment thereof) of a T-even phage. Optionally in the tail fibre or spikeA: the first fragment is a N-terminal fragment of a tail fibre of a tailocin; and B: the trimer comprises a polypeptide (or fragment thereof, optionally the second fragment) of a T-even phage. Optionally in the tail fibre or spike A: the first fragment is a N-terminal fragment of a tail fibre of a T-even phage; and B: the adapter comprises a polypeptide (or fragment thereof) of a tailocin and / or the monomer comprises a polypeptide (or fragment thereof) of a tailocin. Optionally in the tail fibre or spike A: the first fragment is a N-terminal fragment of a tail fibre of a T-even phage; and B: the trimer comprises a polypeptide (or fragment thereof, optionally the second fragment) of a tailocin. Optionally in the chimaera, tail fibre or spike the trimer comprises a gp37 polypeptide (or fragment thereof) and / or the adapter comprises a gp38 polypeptide (or fragment thereof). For example, the adapter has 37, 38, 39 or 40 amino acids. The C-terminus of each polypeptide of the trimer may comprise a C-terminal fragment of a gp37 polypeptide; optionally, wherein the fragment is devoid of residues 1-10, 1-20, 1-30 or 1-40 of the gp37. The C-terminus of each polypeptide of the trimer optionally comprises a gp37 polypeptide (or fragment thereof) that is fused at its N-terminus to a heterologous tail fibre polypeptide. Each polypeptide of the trimer optionally comprises (i) a polypeptide (or fragment thereof) of a first tail fibre that is fused to (ii) a polypeptide (or fragment thereof) of a second tail fibre, wherein the tail fibres are different. The tail fibres are optionally tail fibres of different viruses (eg, different phages) or different tailocins, or one tail fibre is a tailocin tail fibre and the other is a virus (eg, phage) tail fibre; optionally wherein the second tail fibre is a tail fibre of a T-even (eg, T2, T4 or T6) phage and the first tail fibre is a tail fibre of a phage that is not a T-even phage. In an embodiment, (i) is C-terminal to (ii). The first tail fibre may be a tail fibre of a tailocin (eg, R-type pyocin), lambda phage, a Peduovirinae, Punavirus (optionally P1) or Muvirus (optionally P2) and optionally the second tail fibre is a tail fibre of a Tevenvirinae phage (optionally a T2 or T6).The invention further provides:- A virus (eg, a phage) comprising the chimaera, tail fibre or spike as described herein. Preferably, the virus a phage. A library of tail fibres or spikes, wherein each tail fibre or spike is as described herein or comprised by a virus or tailocin described herein, wherein the monomers of at least some of the members of the library differ from each other. A library comprising a plurality of adapter-monomers, wherein each adapter is an adapter as defined herein and associated with a polypeptide monomer, wherein each adapter-monomer comprises the adapter then the monomer in N- to C-terminal direction, wherein the monomers of at least some of the adapter-monomer members of the library differ from each other, optionally wherein each adapter comprises an N-terminal interface that is associated with a polypeptide trimer interface. Each said adapter is optionally fused to a capsid protein of a virus (eg, a phage, such as fused to a phage pIII protein or fragment thereof), wherein the virus comprises a tail fibre comprising (in N- to C-terminal direction) said capsid protein, the adapter and the monomer. A library comprising a plurality of polypeptide monomers, wherein the monomers differ from each other, wherein each said monomer is fused to a protein displayed by a carrier (eg, a virus (such as a phage), cell or nanoparticle). Optionally wherein the monomers are variants of a parental monomer and differ from each other by one or more amino acid residues. The parental monomer may be an Ig or a non-Ig domain, eg, an antibody single variable domain (such as a dAb or VHH). The library may be the product of using error prone PCR to generate said variants. The C-terminal peptide loops of monomers of at least some of the members of any library described herein may differ from each other. Optionally, different members of the library comprise different monomers wherein the monomers are ligand binding sites, the ligand binding sites differing between said members. There is provided: A phage display library, wherein the library is according to any library described herein. A first Clause provides:- A method of selecting a tail fibre or spike sequence, the method comprising contacting a library as described herein with a ligand, wherein the tail fibres or spikes are displayed on carriers, wherein eachcarrier comprises a respective nucleic acid encoding the tail fibre or spike that it displays, wherein monomers of tail fibres or spikes of the library bind to the ligand, the method comprising isolating nucleic acid of a carrier whose fibre or spike monomer bound to the ligand; and determining the nucleotide sequence of the monomer of said fibre or spike and / or isolating said fibre or spike. Optionally, each carrier is a virus (eg, a phage), a tailocin (eg, R-type pyocin), cell or nanoparticle. Any tailocin herein may be a pyocin, eg, an R-type pyocin. The pyocin may be an S-type pyocin. The pyocin may be an F-type pyocin. There is provided:- A method of producing a tail fibre or spike, the method comprising (i) providing a protein expression construct, wherein the construct comprises a nucleic acid that encodes a phage tail or tailocin fibre or spike, the nucleic acid comprising said nucleotide sequence determined by the method of the first Clause; (ii) expressing the tail fibre or spike encoded by the construct; and (iii) optionally isolating the tail fibre or spike. A method of producing a tail fibre or spike, the method comprising (i) contacting a library described herein with a ligand, wherein the monomers are displayed on carriers, wherein each carrier comprises a respective nucleic acid encoding the monomer that it displays, wherein monomers of the library bind to the ligand; (ii) isolating nucleic acid of a carrier whose monomer bound to the ligand; and (iii) determining the nucleotide sequence of the monomer of step (ii); the method further comprising (iv) providing a protein expression construct, wherein the construct comprises a nucleic acid that encodes a phage tail or tailocin fibre or spike, the nucleic acid comprising said nucleotide sequence determined in step (iii) or a nucleotide sequence that differs by no more than 5 codon changes; (v) expressing tail fibre or spike encoded by the construct; and (vi) optionally isolating tail fibre or spike. Optionally, the construct is a plasmid (optionally comprised by a bacterium) or a DNA comprised by the genome of a host bacterium. The construct may be comprised by a plasmid, eg, wherein the plasmid comprises an origin of replication and a phage packaging site (eg, pac or cos). Such a plasmid may be packaged in a virus or phage capsid. The construct may be comprised by the genome of a host cell for expression of the fibre or spike, eg, wherein the host cell is a bacterial cell.The DNA may encode a phage, tailocin or transduction particle when expressed in a host bacterial cell and said step of expressing the tail fibre or spike comprises producing the phage, tailocin or particle in the bacterium; optionally wherein the method comprises isolating the phage, tailocin or particle. In an embodiment, the method further comprises formulating the phage, tailocin or particle with a pharmaceutically acceptable diluent, carrier or excipient, thereby producing a pharmaceutical composition. It will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine study, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims. All publications and patent applications mentioned in the specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications and all US equivalent patent applications and patents are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. Reference is made to the publications mentioned herein and equivalent publications by the US Patent and Trademark Office (USPTO) or WIPO, the disclosures of which are incorporated herein by reference for providing disclosure that may be used in the present invention and / or to provide one or more features (eg, of a vector) that may be included in one or more claims herein. The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and / or the specification may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one." The use of the term "or" in the claims is used to mean "and / or" unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and "and / or." Throughout this application, the term "about" is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects. As used in this specification and claim(s), the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.The term "or combinations thereof" or similar as used herein refers to all permutations and combinations of the listed items preceding the term. For example, "A, B, C, or combinations thereof is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, MB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context. Any part of this disclosure may be read in combination with any other part of the disclosure, unless otherwise apparent from the context. All of the compositions and / or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and / or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims. The present invention is described in more detail in the following non-limiting Examples. EXAMPLES EXAMPLE 1: MATERIALS and METHODS The bacteria and phage strains used in this work is given in Table 1. Media and growth conditions E. coli were routinely cultivated in LB broth (shaking, 250 rpm) or LB agar (LA) at 37°C. E. coli carrying the lambda-red recombination plasmid (pKD46) routinely grown at 30°C with ampicillin. When necessary, culture media was supplemented, ampicillin (amp, 100 µg / ml); spectinomycin (spc, 100 µg / ml), chloramphenicol (cam, 10 µg / ml), zeocin (zeo, 0,7 µg / ml) or kanamycin (kan, 50 µg / ml). The ten-fold dilutions of phage lysate were freshly prepared in SM buffer.Propagation and assays of Tevenvirinae member a184 Phage a184 routinely propagated in 10 ml LB broth in a 50 ml falcon tube. Briefly, an overnight culture of b52 was 1:100 diluted in LB and incubated at 37°C with shaking for 1h. Then, cells were infected with 10 or 100 µl of the a184 (M12AEC00) parental lysate (Gencay et al., 2016). The propagation was allowed to continue up to 4h at 37°C with shaking. Phage lysate was then centrifuged 16.000 x g for 10 min and supernatant was filtered through 0.2 µm syringe filters. For plaque assays, bacterial lawns were prepared on round LA plates by inoculating 100 µl overnight culture of the corresponding strains into pre-tempered (melted and cooled to 45-50°C) 3 ml LB top agar (LB broth supplemented with 0.4% agar) and pouring the mix on to distribute homogenously. Poured plates are allowed to solidify for minimum 10 min. Ten-fold diluted phage lysates in SM buffer were spotted on the freshly prepared bacterial lawns (5 µl) and then, plates were dried in a laminar hood (max.30 min) and incubated at 37°C overnight. After the incubation, formation of plaques was visually evaluated and efficiency of plating (EoP) via plaque forming units per ml (pfu / ml) were calculated by multiplying the number plaques with the factors of dilution and spotted volume. In all EoP analyses, wt background strain b52 was used as control. Knockout mutants Gene knockouts were achieved by introducing an antibiotic resistance marker via electro- transformation of PCR amplicons amplified with homologous arms following lambda red-based recombination (Datsenko and Wanner, 2000). To create the deletion in gene H of P2, a kanR fragment amplified from pRFB110 with primers FO31 / FO32 was transformed to b52 P2 lysogen (b337) with pKD46 plasmid. Colonies were selected on LAkan and correct recombinant was confirmed by PCR with primers FO16 / FO29 and named as b411. For obtaining the deletion in phage receptor Tsx, b52 carrying the pKD46 plasmid was transformed with a cat PCR fragment amplified from pBAD33 backbone with primers FO495 / FO496S. Following transformation of the amplicon, colonies were selected on LAcam. The receptor mutant of native P2 fibre was created in b52 background by amplifying the zeo marker from b337 using primers RfaDup / down, transforming to b52 carrying the pKD46 and selecting on LAzeo. Correct recombinant was determined by PCR and named as b3364 and b2607, respectively. Engineering of DNA cargo with trans-complementing chimeric and native fibre A striking feature of P2 / P4 is that phage P2 can be exploited for its structural components by the satellite coliphage P4 (Six, 1963). The pirating defective phage P4 can de-represses and transactivate chromosomally integrated helper prophage P2 to initiate lytic cycle and express structural proteins by the activity of delta and psu (Halling et al., 1990; Linderoth et al., 1997). Meanwhile, P4 sid modifies P2 capsid to host approximately 1 / 3rdsmaller P4 genome carrying P4 pac signal instead of the nativeP2 genome (Marvik et al., 1995). Consequently, P2 virions with smaller P4 size heads are formed. Hence, the plasmid p360 that was carrying the 2291 bp fragment of sid, delta, psu and pac signal of P4 (NC_001609: 5543-7833 bp) under the arabinose promoter (Para), along with markers of spectinomycin resistance (aadA) and sGFP was reverse amplified using primers FO510 / FO511 forming the backbone for P2 activation and P4 size (~11kb) DNA cargo packaging. This backbone was then ligated to DNA encoding a chimeric fibre fragment created as described below. Chimeric fibre fragment was created stepwise and ligated to the above backbone using InFusion™ cloning according to manufacturer’s recommendations. A separate pBAD33-based plasmid (p312), was created by placing DNA encoding the wt P2_H-G downstream of a DNA sequence of Parausing PCR fragment from b337 with primers FO29 / F15O and reverse amplified fragment obtained from pBAD33 using primers FO27 / FO45. Transformants were selected on LAcam and sequence was confirmed with primers pBADf / FO43. Then, p312 was reverse amplified using FO447 / FO448, corresponding gp37-gp38 and gp57a was amplified from the phage a184 using primers FO449 / FO450 and FO451 / FO452, respectively, and three fragments were fused together, transformants were selected on LAcam and sequence of p1188 was confirmed by primers FO16 / FO453. p1188 was then reverse amplified by FO452 / FO492 and self-fused to create p1229 by omitting gene G already available lysogen b411. Then the PCR fragment comprising the translational fusion of wt P2_H1-502- a184_gp37931-1109, followed by a184_gp38, ribosomal binding site and a184_gp57a under the Parafrom plasmid p1229 was amplified using primers FO512 / FO513 fused to the DNA cargo backbone, transformants were selected on LAspc and translational fusion was confirmed on p1267 (Figure 3) using primers FO429 / FO453. p1267 was then transformed into b411 and named as b3445. To create the control native H fibre the corresponding region section was repaired in. This was achieved by amplification of p1267 with FO447 / FO496L and infusion of respective region amplified from b337 with FO577 / FO578, selecting on LAspc. Upon confirming the correct sequence with primers FO16 / FO453, p1371 was transformed to b411, selected on LAspc and named as b4202. Harvesting and transduction assay of virions A streak of strains b3445 and b4202 grown overnight on LAspc plates was inoculated in 50ml LBspc in e-flask, allowed to grow to an optical density of OD600: 0.3 – 0.4 in a shaking incubator at 37°C and induced with 1% arabinose after transferring a 10ml aliquot into 50ml falcon tube. Culture followed for formation of lysis by reduction of turbidity, 2h later DNAse was added (1:10000 v / v) and approximately 3h later, centrifuged at 17.000 X g and supernatant was filtered through 0.2 µm syringe filter. This lysate was then subjected to a transduction assay in which, 100µl overnight cultures of strain b52, b2607 and b3364 in LB were mixed with 100µl aliquots of the lysate in an Eppendorf tube and incubated at 37°C thermo-shaker for 1h. Then, 10-fold serial dilutions from each tube were made in PBS and 5µl of each dilution were spotted on LAspc plates. After drops were soaked, plates wereincubated in 37°C overnight. Next day, presence or absence of green fluorescents colonies were inspected in a UV-visualizer with orange filter. RESULTS Characterization and selection of a184 gp37-gp38 for fusing to P2-H Receptors of wild-type phages are routinely determined by comparing efficiency of plaquing of phages on wild-type strain and its isogenic receptor mutants. a184 was determined to be dependent on outer membrane nucleoside transporter Tsx, as it formed plaques on b52 but was unable to form any plaques on b3364 (b52∆tsx::cat), similar to that observed for phage T6 (Trojet et al., 2011). This analysis confirmed that a184 RBP gp38 is dependent on presence of Tsx (Figure 4A). To engineer the monomeric RBP gp38 on a trimeric P2 phage fiber H (NP_046775.1), a functional translational fusion of H N-terminal and T2 / T6-like gp37 with C-terminal PF13884 domain was sought. First, the different sections of H (~100 residues) were used as query and blasted against a collection of in-house T2 / T6-type gp37 amino acid sequences available in SNIPR Biome phage bank (n:23) using Geneious Prime (2021-03-21, Biomatter) default parameters (BLOSUM62; Gap cost: 11 1; Max E-value: 0.05; Word size: 6). Second, a PFAM database (version 34.0) search using PF13884 domain (Accession date: 18 May 2021) was conducted to pool more amino acid sequences of fibers and spikes of phages under Caudoviricetes class. Then, sections of blast hits (similarity windows) were pairwise aligned using default ClustalO algorithm (Madeira et al., 2019) also available in Geneious Prime, and inspected manually. The downstream residue on the a184 gp37 flanking 6 identical residues in the alignment of H and a184 gp37 was selected as the fusion point (Figure 2) and corresponding gene segment was introduced along with the cognate gp38 and gp57a genes. LPS-dependent native and Tsx-dependent chimeric P2 / P4 particles Upon harvesting the native (from b4202) and chimeric (from b3445) P2 / P4 virions, a transduction assay was performed using wild type b52, LPS mutant b2607 and Tsx mutant b3364. Ten-fold dilutions of bacteria-phage mix were plated on LAspc and next day, and colonies with green fluorescence observed, as shown in Figure 4B. The DNA cargo was not delivered to the LPS mutant when virions had their native fibres, demonstrating the LPS-dependency of native H fibre. With chimeric fibres however, the DNA cargo was successfully delivered to both b52 and the LPS mutant, while there was no DNA deliver to the Tsx mutant. These results clearly demonstrate the switch of receptor dependency from LPS to Tsx confirming the gp38 mediated Tsx-binding of chimeric fibres. Thus, using the present invention we were surprisingly able to change specificity of the tail fibres by creating synthetic fusion between portions of trimers from different wild-type phage fibres, where the C-terminal portion carried a gp38 monomer that recognises Tsx. This finding opens up the possibilityof creating repertoires of viruses that differ in their gp38 sequences (presented distal to common trimer attaching to the baseplate). With routine screening against receptor protein, it is then straightforward to select for gp38 members of the repertoire library that have desired binding to receptor. Subsequently, a nucleotide sequence encoding a selected gp38 can be used to produce synthetic tail fibres on phages or tailocins. REFERENCES Bartual SG, et al. (2010). PNAS, 107, 20287-20292. Datsenko KA, Wanner BL (2000). PNAS, 97, 6640-6645. Drexler K, et al. (1989). J Mol Biol, 207, 797-803. Dunne M, et al. (2018). Structure, 26, 1-10. Fekete RA, Chattoraj DK (2005). Mol Microbiol, 55, 175-183. Haggård-Ljungquist E, et al. (1992). J Bacteriol, 174, 1462-1477. Halling C, et al. (1990). J Bacteriol, 172, 3541-3548. Hashemolhosseini S, et al. (1994). J Mol Biol, 241, 524-533. Gencay YE, et al. (2016). J Food Safety, 36, 120-131. Ghequire MGK, De Mot R (2015). Trends in Microbiol, 23, 587-590. Koskella B, Brockhurst MA (2014). FEMS Microbiol Rev, 38, 916-931. Linderoth NA, et al. (1997). Virology, 227, 131-141. Letarov AV, Kulikov EE (2017). Biochem, 82, 1632-1658. Leiman PG, et al. (2010). Virology J, 7, 355. Marvik OJ, et al. (1995). J Mol Biol, 251, 59-75. Madeira F, et al. (2019). Nuc Acid Res, 47, W636-W641. Montag D, et al. (1987). J Mol Biol, 196, 165-174. Morita M, et al. (2002). FEMS Microbiol Lett, 216, 243-248. Morona R, Henning U (1984). J Bacteriol, 159, 579-582. Nobrega FL, et al. (2018). Nature Rev Microbiol, 16, 760-773. North OI, et al. (2019). Nat Microbiol, 4, 1645-1653. Riede I, et al. (1987). J Mol Biol, 194, 23-30. Six, EW (1963). Bacteriol Proc, 138. Stuitje AR, et al. (1981). Nature, 290, 264-267. Tetart F, et al. (1998). J Mol Biol, 282, 543-556. Trojet SN, et al. (2011). Genome Biol Evol, 3, 674-686. Williams SR, et al. (2008). Appl Environ Microbiol, 74, 3868-3876. Yoichi M, et al. (2005). J Biotech, 115, 101-107.Table 1. Bacterial strains, phages and plasmids Strains Relevant information b52E. coli C1a, phage propagation hostb337 b52 P2 lysogen, core mutant (∆rfaD::zeo) b411fibre knockout mutant b3445 b411 p1267, chimeric fibre P2 / P4 production host b4202 b411 p1371, native fibre P2 / P4 production host b2607 B52∆rfaD::zeo, receptor knockout mutant of native fibre b3364 b52∆tsx::cat, receptor knockout mutant of chimeric fibre P4 Satellite phage P4 (Accession no: NC_001609) a184Tsx-dependent T-even virus (M12AEC00, Gencay et al. 2016)Plasmids pKD46 Lambda red recombination plasmid, amp (Datsenko and Wanner, 2000) pRFB110 kan (kanR) fragment (Fekete and Chattoraj, 2005) pBAD33 cat (camR) fragment p312 Para-P2H-G, cat, p15a ori p360 Para-P4 sid-delta-psu-pac signal (NC_001609: 5543-7833 bp), araC, aadA (spc), sGFP, high copy CloDF13 ori (Stuitje et al.

[1981] ) p1188 Para-P2H_a184-gp37-gp38-gp57a-P2G, cat, p15a ori p1229 Para-P2H_a184-gp37-gp38-gp57a, cat, p15a ori gp37-gp38-gp57a, araC, aadA, sGFP, CloDF13 ori (Figure 3)Table 2: Sequences for Example 1 Nucleotide sequences are written in 5’ to 3’ direction; amino acid sequences are written in N- to C- terminal direction. Primers SEQ ID Primers Sequence (5’ to 3’) NO: 164 pBADf ATGCCATAGCATTTTTATCC 165 FO16 TTGTTTTTGGATTACCTGACTTAATGTTCT 166 FO27 TACTAGACCTCCTTACGGGTATGGAGAAACAGTAGAGAGTTGFO29 GTTTCTCCATACCCGTAAGGAGGTCTAGTATGAGCATAAAATTCAG A FO31 CGGTTTACCCCGGATAAGTGAGGAATAATGAGCATAAAATTCAGAA CCGTTATCACCACTGAATTAGCCATGGTCCATATGAAT FO32 TGACTTAATGTTCTTTAAATGCTGCATAACTTACACCTGCGCAACGT TATACCATGTGCCTTGAGCGATTGTGTAGGCTGG FO43 TACTGTCCGTCGTGTGGACA FO45 AGCAGGGAGCAGAGCTTAAGGCCA FO150 GCTCTGCTCCCTGCTTTATTGCGGCATTTCCGGCCATTCAG FO318 TGGCAGCCGGTGCGGT FO319 AGCCGGTAGAGCGAACGTTG FO429 CAGGAGAGCGTTCACCGAC FO447 TCCGGTATCATTATCACCAAGAACAATAGAG FO448 TTGCGCAGGTGTAAGTTATGCAGCATT FO449 TTGGTGATAATGATACCGGATTAGTTCATGGTGGTGACGGCCG FO450 ACATACTAGACCTCCTTACGTTATACTCTTGGACCATATATTGCTCC AACG FO451 CGTAAGGAGGTCTAGTATGTCTGAACAAACTATTGAACAAAAACTG TCTG FO452 CATAACTTACACCTGCGCAATTATTCTTCATCTTTTGCTTCATCAGCA GATTC FO453 TTGTTAATGCCGTCATTAATGGCTGT FO492 AAACCAGACCCAGAGCTACGATGTTATCAGTGTTGATGCCAGCGTC ACGAGTGAACTGGTTAGACAGCTCAAGCTAGCAGAGTT FO495 CCGGTGCGGTACTGGCGCTCTCTTCGTCTTTTACTGTCAACGCAGCT GAACGTTGATCGGCACGTAAGAGG FO496 GTAACCTACTACCAGGTAACCACCCCAGCCGGTAGAGCGAACGTTG AAGTTGCTTCATCCGCTTATTATCACTTATTCAGG FO510 TGAAAGCTGTAATTTGGACTCACAAAGAAAAAAC FO511 AAGCGTCAGGTAGGATCCGCATACTTCTATTCTACTCTGACTGCAAA CCAAA FO512 GCGGATCCTACCTGACGCTTTTTATC FO513 AGTCCAAATTACAGCTTTCAGCAAAAAGGCCATCCGTCAGGATGGDNA SEQUENCES DNA sequence of a184-gp38 [SEQ ID NO: 190] ATGGCAGTAACAGGACCGTGGGTAGGATCGTCTGCAGTAGTTAATACAGGACAAAATTG GATGGGTGGTGCCGCGCAGAGATTGAGAATGGGAATTCCGTTTTGGATGAGTAATATGA TAGGTAGATCTGTTGAAATAATTCACACGCTTGGAGCAGACCATAACTTCAATGGTCAAT GGTTCCGAGATAGATGTTTTGAGGCAGGTAGTGCACCTATAGTGTTTAATATCACTGGAG ATTTAGTATCATATTCTAAAGATGTTCCTTTATTCTTCATGTATGGAGATACACCGAATGA ATATGTTCAGTTGAATATACACGGCGTAACGATGTATGGCCGTGGCGGTAATGGCGGTA GCAATAGTCCTGGTTCAGCTGGAGGTCATTGTATTCAAAACGATATTGGTGGGAGACTAA GAATTAATAATGGCGGAGCTATTGCAGGCGGCGGCGGTGGCGGCGGTGGCGGATATTAT TCTCCTTTTTCACAAATGAGATTGACTTTTGGAGGTGGCGGCGGGCGTCCGTTTGGCGCA CCGGGCGGATCTATTGATATGCAATCAGGAGCAACTGCTGGTACTATTTCTGCGCCTGGC GCAGGGTCTGTGAACGGTATCTATAGCGGCGGTGGCGGTGGCGAAGTTGGCTCCGCAGG AGGTAGATGTAATATTCGTGGTCAAGGATATGAATACGATGGCGGAGCTGCTGGTTATG CCGTCATAGGGTCTACACCGACATGGCAAAACGTTGGAGCAATATATGGTCCAAGAGTA TAA DNA sequence of a184-gp57a [SEQ ID NO: 191] ATGTCTGAACAAACTATTGAACAAAAACTGTCTGCTGAAATCGTAACTTTGAAGTCTCGT ATTCTTGATACGCAGGACCAGGCGGCGCGTCTGATGGAAGAATCCAAAATTCTGCAAGG AACTTTGGCTGAAATTGCTCGCGCAGTAGGTATCACTGGCGATACTATCAAAGTTGAAGA AATTGTTGAAGCTGTCAAGAATCTTACTGCTGAATCTGCTGATGAAGCAAAAGATGAAG AATAA AMINO ACID SEQUENCES Amino acid sequence of the chimeric P2 / P4 fibre (translational fusion junction of P2-H1-502and a184-gp37930-1109is underlined) [SEQ ID NO: 192] MSIKFRTVITTAGAAKLAAATAPGRRKVGITTMAVGDGGGKLPVPDAGQTGLIHEVWRHAL NKISQDKRNSNYIIAELVIPPEVGGFWMRELGLYDDAGTLIAVANMAESYKPALAEGSGRWQ TCRMVIIVSSVASVELTIDTTTVMATQDYVDDKIAEHEQSRRHPDASLTAKGFTQLSSATNST SETLAATPKAVKAAYDLANGKYTAQDATTARKGLVQLSSATNSTSETLAATPKAVKTVMDE TNKKAPLNSPALTGTPTTPTARQGTNNTQIANTAFVMAAIAALVDSSPDALNTLNELAAALG NDPNFATTMTNALAGKQPKDATLTALAGLATAADRFPYFTGNDVASLATLTKVGRDILAKS TVAAVIEYLGLQETVNRAGNAVQKNGDTLSGGLTFENDSILAWIRNTDWAKIGFKNDADGD TDSYMWFETGDNGNEYFKWRSRQSTTTKDLMTLKWDALNILVNAVINGCFGVGTTNALGGSSIVLGDNDTGLVHGGDGRINMVANGIHIANWGAGYQSHPGLWDSTGAFWTEVGRAIVSHG HLVQANDSYSTFVRDVYVRSDIRVKKDLVKFENASEKLSKINGYTYMQKRGLDEEGNQKW EPNAGLIAQEVQAILPELVEGDQDSEALLRLNYNGVIGLNTAAINEHTAEIAELKSEIEELKAL VKSLLK Amino acid sequence of a184-gp38 [SEQ ID NO: 193] MAVTGPWVGSSAVVNTGQNWMGGAAQRLRMGIPFWMSNMIGRSVEIIHTLGADHNFNGQ WFRDRCFEAGSAPIVFNITGDLVSYSKDVPLFFMYGDTPNEYVQLNIHGVTMYGRGGNGGS NSPGSAGGHCIQNDIGGRLRINNGGAIAGGGGGGGGGYYSPFSQMRLTFGGGGGRPFGAPGG SIDMQSGATAGTISAPGAGSVNGIYSGGGGGEVGSAGGRCNIRGQGYEYDGGAAGYAVIGST PTWQNVGAIYGPRV Amino acid sequence of a184-gp57a [SEQ ID NO: 194] MSEQTIEQKLSAEIVTLKSRILDTQDQAARLMEESKILQGTLAEIARAVGITGDTIKVEEIVEAV KNLTAESADEAKDEE.)nrioetsodripca nooinsiufma glnait clit usneerdIeh.t )tnnie nmoi ntgcil naujf(ostennii lopn .m tot i 4oselou bbfe a(Tnilepnitmoa nrxpewoHev his2Ptaerdn anraet slec)t anneete2au3mcqn ieg dsin nli ias etfowoorern r pinlA oip .oe sut(nifelgcelnit nd lusedtui snqmerie eos e hPdihtTnca no .oit enc oonraitnium) ceJ a ”ri& 7+“ dls3tp aanghtinie newmrme netng witle w -ohCoAbs se t( tns -cn edeumiNcaeraqnegiSl oansiec:3ecmnaeen ule rbu alqaq iesm llTeSisA 5Table 4: Protein H / gp37 Fusion Protein Sequences Sequences are written in N- to C-terminal direction. Double underlined amino acid sequence corresponds to N-terminal sequence of a P2 H polypeptide; non-underlined amino acid sequence corresponds to C-terminal sequence of a gp37 polypeptide. SEQ ID Amino Acid Sequence of Fusion Protein NO: 1 GSSIVLGDNDTGLVHGGDGRINMVANGIHI 2 NTSTKNITFNLWGASTRPVVAELGDESGWHWYTQRAGGPGTELIDFAINGTVKP 3 NTSTKNITFNLWGASTRPVVAELGDEAGWHFYSQRAGGPGTELIDFAINGTVKP 4 LGGSSIVLGDNDTGFKWHQDGYYFSVNNGTKTFLFSPSETTSLRKFVAGYS 5 LGGSSIVLGDNDTGFKQNGDGYYFSVNNGTKTFLFSPSETTSLRKFVAGYS 6 GCFGVGTTNALGGSSIVLGDNDTGFKNDGDGMFSVMANSRALVNY 7 GCFGVGTTNALGGSSIVLGDNDTGFKQNGDGIFSVMANSRALVNY 8 GVGTTNALGGSSIAIGDDDTGLVHGGDGRINMVANGSHI 9 GVGTTNALGGSSIVLGDNDTGLVHGGDGRINMVANGSHI Table 5: Sequences Shown in Table 3 SEQ ID NO: 10 GACVVIGDNDTGLVHGGDGRINMVANGIHI 11 GSSIVLGDNDTGFKQNGDGILDVYANSQRV 12 NTATSSFNIRAWGSDSRKQVLECADESGWHWYTQRAGGPGTELIDFAINGTVKP 13 NTSTKNITFNLWGASTRPVVAELGDEAGWHFYSQRNTDNSVIFAVNGQMQP 14 LGPSSIALGDNDTGFKWHQDGYYFSVNNGTKTFLFSPSETTSLRKFVAGYS 15 LGGSSIVLGDNDTGFKQNGDGILDVYANSQRVFRFQNGVAIAFKNIQAGDS 16 GSSGTGFVSGMGEGSLALGDNDTGFRNDGDGMFSVMANSRALVNY 17 GCFGVGTTNALGGSSIVLGDNDTGFKQNGDGILDVYANSQRVFRF 18 GVGTIPVWGGASIAIGDDDTGLVHGGDGRINMVANGSHI 19 GVGTTNALGGSSIVLGDNDTGFKQNGDGILDVYANSQRV 20 GDNDTG 21 LGDNDTGFK 22 LGDNDTGF 23 GVGTareamihG G G G G G GcD D D D D D D G GybG G G G G G G D D G G G G G G G GIdG H H H H H H H G G N N N GesiVVrLV V V V VH H N VVA A A A N N N N N A A A AApLL L L L LG G GG G G GLGLV V V V V V G M M VVY moT TTTcD D DDT T TM M M MMV V D D DT TN N NN ND DeN N D DI I IINIDcN N N NNN NR R RR L L L LD D DDD G GGI I I I InD D D D G G DDG G G G G GeuqLGLGLGLGLGLLGIGIGD D D D D D D G G G GeV V V V V V V V VG G G GsI I I I I IN N N N N N N N N)SI I ISSSSSSSSSSSS S SQ Q Q Q Q Q Q Q QcS S S(G G G G G G G G GKFKFKFKFKFKFKFKFKFfo )ehOc(tN geniDI cnsi nerQupoitcEqmnSesocuj061626364656667686960717273747576777fe oclnnaieGenuitoG Dqm rer pG G D D GseG G t- noG D G G D G G G HdiisG HVNc Cay uD G G H A N f G D GVLo lG H enniG D G G HVVL LGV A N T M V A N53i tai nD G G H G G HVLLG GGT TD NIM V A N A N mdAeoitG HVVLGTD D N N DRNIM V A N N M V)mcnHVVIL LGTD N GRTD N D DGIDIA N M V N Gb(m u V G GGRI NM A N ij LGTD N D GIV G D GR IN M V A seDcI fnQoeuEOqSNe)Sb(243444546474849405152535455565758595fe oncl inaenetui orqmer psetnGY -oiiT TV Vdc Nsay uD D D D D D f N N N NIL L L Lo lentniD D D D DI I I Iiai nGLG G G G GG G G G G G D VLVLVLVLVLVLD D D D D D VVG G G G G G md oiG GAe tcI I I I I I I I IN N N N N N N N N)mnSSSSSSSSSSSSSSSSSSQ Q Q Q Q Q Q Q Qa(miujG G G G G G G G GKFKFKFKFKFKFKFKFKFONseDcIneQuESfqoe)Sa(425262728292031323334353637383930414GCCCC G GAAG A C ACC G TGC C GAA C GT C TCCT A CCGCT ATG GTA ATA GACTGC C CG AA A AGG G G A ATA G A GCG C GGCTCG G ACCCGC A AGAGT ATCC CAA TCTGTATG AATGG ACGA G CCG AGACACTC G ATTC TA GC C C CG GCA TTCA A A ATA A G G G GG TG AT CG GTTA GCG G G G GG CT C CAA AATCACA GAACTTGT TA AACA ACA AC G ACATT G GCCG GG GCC G GGC CGCC TA GC TT ACCTGCTC CG GCGCA GTGT TC ACGAA C GG CAC CTCACCGTTT G TC TAGCACGG A GCA GC TGGGCTTGCAGTACA AG C TGCGTATAA A AC TA A C CTAAC T CGCG G A A G A ATC C T TATCA AGGCAC GAGG TTG AG GA G A A GCTTGGCT CCG GC TGGCC CAA AC TA G G GCTT CAAAC CGTG GCTCT G ATTCG AG CCGTGG TTAG A GCCG A AAG AGT TTT GCCAC CG A T G G A AC AG A CG CACCGAAA TGCCATGCACGCCGCG A G G G TTACACAG GCGG GACG A GGGTG A ACC TTCCA CCCGACCGAAA CACAT TAGC CA ACA A GTGC T CCCT ATG ATCCACTCG GCC GG GT GA A GC TG TC TTCTT CCG A CTGG AG GG CGACG ACTG G AC CC ATG GCGTAT G AC ACG C GCATTA ATCATCGGAC CATAC TCCACATGA GCGCATCG T GT GG C A A C ATATT TT CG A GAATAC TGC T CA AATCG ACGTT A GA GGA G A AT CTAGT GCGG GAC TGCG TCTATA TCGTATGCT TAATGGACGA G GTA T GCAG ACCGC GCA G GAG G G C GC AC CA G TTTCCA ACG A GCCCCC TGC CTTG GTG ACG AGCAGT A GGTCCAA CG ACG G C GCGTA G GACTGCAC CTAC TGCA TCG A G GAACA G ATGTCTTGAGC T TCC A ACA GCC A A A ACG ACG ACGCTCATAGGT CA T G GG GAGATA G TCATG A GCAGGATA TCAAC6A3TGGC TATGTTTA G GCTCGTATA ACCC AGTG ATG A A GTGGCCG G A GGACAAC G GGA ACCTAATCG G A GTA GCTTGTGCA A ACGGTTG A A T A ACG A A G ATA G AGA G GCGTTCCG G AC GA ACCCT GC AGGTCeAcCG G G GGAT CA AGCACACGTG A neG GCC ATu AC C CA G ACA GCA AC GG A AT GC TT G G ACATCT CG ACqGeS T CCTC TGT CTA AA CCACA GT AG TAGT CGCCGT A G GCT G AGC C CA GCG G A CAC GCCAC AGC A G A cifsiro 9e n0mi o1i1- s03hcu79fel3ht apf ng- ooit4 )a8 ~~eecls1c nadhtn nne oie au tuqrt(nia2w dq pe iers e05Scr - etAbi1ace sr eNfH iD2-2dnbDP P iiFli:aOT N:7DIelbQa ES8T 7CT TCC A C TT T AA A AGAATCGT CA A A ATA A A GGT A G G G G A G G AGT GA A AA A AG GTCT A TTGTG A GAACA TTCAGC CCTGATCGAATATCTTTTA AT CGTGAGCTTAACGT CCA TTT TAATAGG A GT TAT CAAATA A GC GTT A A ATATTCG GT T CA TG ATGT GC T A GA A GAC C C CAT TA AA GCGCGTCT TC TAT CG AGTGTGTGTTG GTAGCTG ATGA ACAG ATG ACA A ACT TGCAAAACAG A GG GTTC TCA A GTCGGCTG GTTA TT ATTATGCGAATTAG CCA AAGTA AG GTATT T ATATGC CGCTTT T TAGACG AA GATGACGTCG GGT TTGCACG ATG GTGACC CA A A A AG G A GCGT TA AC CAT G G T TAGTAGT TAC C T T TGTCCG A ATA ACG GA ATT G G ATG ACA ACG GTT T C CGTCA A GTA G G GT~A GTTA G G A GCA GT TATAT~G ATG A AC TTTATA G A A A A A GAATATT G G GGA AACA GAG G GTGCG TCGAGCG TT T GAT TAAGTACCCC T CA GTACG AG A GC GTAA AATT CAT A ATCTTATTAAGTAAGTGTA TACCA ACGTTG AT CGACGT GA TCA ATAGTAA T ATC TGATATAT T TAGTGGT G GCCG AATAGCACG ACTGTACTTA GTAAG A TAA A A ACTAķATGijGGC T CAG TATTG ACTA T T GT TATCT CCGT T T TATTACC CTAGG G A TA TT T CT TGTTAAGT A AAACCACATC GGTATTG GCT GG ATTGTG T GAACCGA ACGCCC TATG ATG A GTG A AATTACATT GA AAG GG G T ATTCA GTC ACCTCAGG ATGA ATGCTCTTA T A T A A G GT C T CACG GCTTSNB0016-1 GB Table 6: Adapter, Linker & Monomer Sequences SE DESCRIPTI SEQUENCE Q ON ID NO: Adapter MAVTGPWVGSSAVVNTGQNWMGGAAQRLRMGIPFW 79 sequence MSN Adapter MAVQGPWVGSSYVAETGQNWASLAANELRVTERPFW 80 sequence ISS Adapter MAIVGVPGWIGESAVNETGQRWMDAAMRAVHVSVP 81 sequence GWMSSM Adapter MAVVGVPGWIGSSSVNETGQRWMSQAAGQLRLGVPC 82 sequence WMSQ Adapter MAVEGPWVGWSARVQTGDPWMGGAAQRLRMGIPFW 83 sequence MSNM Adapter MAVTGPNVGSSAKAVTGESSMIAAGAKLRLGTPFMMS 84 sequence S Adapter MAVTGPWVGSSAKATTGERWMKEAGAKLRLGTPFW 85 sequence MSN 86 Linker FAGRSKEI 87 Linker MAGQSVYN 88 Linker MIGKATEV 89 Linker FAGRSREI 90 Linker LAGKSKGL 91 Linker LVGKSREQ 92 Linker LAGKSKEA 93 Linker MIGKSVFH 94 Linker MIGRNVWN 95 Linker MIGRSVFN 96 Linker MIGKSKWH 97 Linker LIGRSKWH 98 Linker MIGQSVFH 99 Linker MIGRSVEI 100 Linker LAGKSKEV 101 Linker MAGQSKEV 102 Linker MAGKSVEKSNB0016-1 GB Linker MAGRSKES Linker FAGKGEIT Linker MVGRSREI Linker FIGRSKEE Linker FAGLSKEE Linker MAGQSKEI Linker QAGKSVEQ Linker MGGRSKEI Linker MAGQSKEF Linker LAGCSKEI Linker LAGRSKEI Linker FSGRSRKI Linker MAGRSKEI Linker LAGRSTEI Linker MAGRSKEV Linker LAGQMVEI Linker MANQSKEI Linker MVGLSKEV Linker MVGKSKEL Linker MIGRSVEV Linker LAGRSANC Linker MNGRSVEV Linker LIGRSREV Linker MANQSVYN Linker FAGRSKEE Linker MVGRSKEI Linker LAGKSRSF Linker LIGRSKEV Linker GGGGS Linker GGGGSGGGGS Linker GGGGSGGGGSGGGGS Linker GGGGSGGGGSGGGGSGGGGS Linker GGGGSGGGGSGGGGSGGGGSGGGGS Linker AGAGAG Linker GAGAGAGAGAGAGASNB0016-1 GB Linker LSRFFHAEL Linker VFNQRKEHKGYMLA Linker IPQGRSHPVQPYPGAF Linker PAVPPP Linker EAAAKEAAKEAAK Monomer IHTLGADHNFNGQWFRDRCFEAGSAPIVFNITGDLVSY SKDVPLFFMYGDTPNEYVQLNIHGVTMYGRGGNGGS NSPGSAGGHCIQNDIGGRLRINNGGAIAGGGGGGGGG YYSPFSQMRLTFGGGGGRPFGAPGGSIDMQSGATAGTI SAPGAGSVNGIYSGGGGGEVGSAGGRCNIRGQGYEYD GGAAGYAVIGSTPTWQNVGAIYGPRV Monomer IWEWTGENHSFNKDWLIGELRNRGGTPVVINIRAHQVS YTPGAPLFEFPGDLPNAYITLNIYADIYGRGGTGGVAY LGGNPGGDCIHNWIGNRLRINNQGWICGGGGGGGGFR VGHTEAGGGGGRPLGAGGVSSLNLNGDNATLGAPGR GYQLGNDYAGNGGDVGNPGSASSAEMGGGAAGRAV VGTSPQWINVGNIAGSWL Monomer YLSIGANHNYDRNSLINWMRAQGGAPVVITITGDLVSN STGNACLEFPSDLPNAYIQLIINSGVTVYGRGGNGSTNS SAGGNGGTAIHNAAGTKLRIRNNGAIAGGGGGGGAAS LKNSYPTNGSCGGGGGRPFGVGGKIGSDSILSGSNASL TDAGTGGTTFQYGAGNGGNVGAGGGRGWGKNVYTS EGGAAGAAVTGNAPNWQNVGTIYGSRV Monomer IHTVSANHNFNGQWFRDRCFEAGGAPIVFNIVGDIVSY SKDVPLFFMYGDTPNEYVVLNIHGGVHMWGRGGNGG SNSPGSAGGHCIQNDIGGRLRINNGGAIAGGGGGGGGG YYSPFPQMRLTFGGGGGRPFGAPGGSINMQSGATGGTI SSPGSGSVNGIYNGGNGGEVGSAGGRCNIRGQGSEYD GGAAGYAVIGSAPTWQNVGAIYGPRV Monomer IHTLGADHNFNGQWFRDRCFEAGSAPIVFNITGDLVSY SRDVPLFFMYGDTPNEYVQLNIHGVTMYGRGGNGWA AGAIGASDGGVCIQNDIGGRLRINNGGAIAGGGGGGG GYSQANNWAGKYVCGGGGGRPFGLGGNNGARWPGG NASLTAPGAGGNTGQYWAGGGGEVGQPGQYANPGN GYSTPPTNPGAAVAGSAPTWQNVGAVYGSRVSNB0016-1 GB Monomer ASITISGNNPATGARVRGAWITKNCASWNVKLDARGS LSGIWETGFNLVAFGLAEPSRWDGYNDALVLEGSGNF NVNWRVDTEDGRQWHFVSSRDYMGRRCYNCTDNNG FWDWLYGNDGRTFQLSFTAY Monomer ASITISGNNPATGPKVRGAWKDKNSASWNVLLDARGA LSGIWETGFNLVAFGLSEPSKTTGYNDAIVLEGSGNFN VNWRVDTEDGNQFHFNSSRDHRGRRCYSCTDNNAFW NWLYANDGRTFQMSFTAY Adapter MAVTGPWVGSSAVVNTGQNWMGGAAQRLRMGIPFW (underlined)- MSNMIGRSVEIIHTLGADHNFNGQWFRDRCFEAGSAPI linker (bold VFNITGDLVSYSKDVPLFFMYGDTPNEYVQLNIHGVT italic)- MYGRGGNGGSNSPGSAGGHCIQNDIGGRLRINNGGAI monomer AGGGGGGGGGYYSPFSQMRLTFGGGGGRPFGAPGGSI DMQSGATAGTISAPGAGSVNGIYSGGGGGEVGSAGGR CNIRGQGYEYDGGAAGYAVIGSTPTWQNVGAIYGPRV Adapter MAVQGPWVGSSYVAETGQNWASLAANELRVTERPFW (underlined)- ISSFIGRSKEEIWEWTGENHSFNKDWLIGELRNRGGTP linker (bold VVINIRAHQVSYTPGAPLFEFPGDLPNAYITLNIYADIY italic)- GRGGTGGVAYLGGNPGGDCIHNWIGNRLRINNQGWIC monomer GGGGGGGGFRVGHTEAGGGGGRPLGAGGVSSLNLNG DNATLGAPGRGYQLGNDYAGNGGDVGNPGSASSAEM GGGAAGRAVVGTSPQWINVGNIAGSWL Adapter MAIVGVPGWIGESAVNETGQRWMDAAMRAVHVSVP (underlined)- GWMSSMAGQSKEIYLSIGANHNYDRNSLINWMRAQG linker (bold GAPVVITITGDLVSNSTGNACLEFPSDLPNAYIQLIINSG italic)- VTVYGRGGNGSTNSSAGGNGGTAIHNAAGTKLRIRNN monomer GAIAGGGGGGGAASLKNSYPTNGSCGGGGGRPFGVG GKIGSDSILSGSNASLTDAGTGGTTFQYGAGNGGNVG AGGGRGWGKNVYTSEGGAAGAAVTGNAPNWQNVGT IYGSRV Adapter MAVVGVPGWIGSSSVNETGQRWMSQAAGQLRLGVPC (underlined)- WMSQFAGRSREIIHTVSANHNFNGQWFRDRCFEAGGA linker (bold PIVFNIVGDIVSYSKDVPLFFMYGDTPNEYVVLNIHGGSNB0016-1 GB italic)- VHMWGRGGNGGSNSPGSAGGHCIQNDIGGRLRINNGG monomer AIAGGGGGGGGGYYSPFPQMRLTFGGGGGRPFGAPGG SINMQSGATGGTISSPGSGSVNGIYNGGNGGEVGSAGG RCNIRGQGSEYDGGAAGYAVIGSAPTWQNVGAIYGPR V Adapter MAVEGPWVGWSARVQTGDPWMGGAAQRLRMGIPFW (underlined)- MSNMIGRSVEVIHTLGADHNFNGQWFRDRCFEAGSAP linker (bold IVFNITGDLVSYSRDVPLFFMYGDTPNEYVQLNIHGVT italic)- MYGRGGNGWAAGAIGASDGGVCIQNDIGGRLRINNG monomer GAIAGGGGGGGGYSQANNWAGKYVCGGGGGRPFGL GGNNGARWPGGNASLTAPGAGGNTGQYWAGGGGEV GQPGQYANPGNGYSTPPTNPGAAVAGSAPTWQNVGA VYGSRV 154 Adapter MAVTGPNVGSSAKAVTGESSMIAAGAKLRLGTPFMMS (underlined)- SMIGRNVWNASITISGNNPATGARVRGAWITKNCASW linker (bold NVKLDARGSLSGIWETGFNLVAFGLAEPSRWDGYNDA italic)- LVLEGSGNFNVNWRVDTEDGRQWHFVSSRDYMGRRC monomer YNCTDNNGFWDWLYGNDGRTFQLSFTAY 155 Adapter MAVTGPWVGSSAKATTGERWMKEAGAKLRLGTPFW (underlined)- MSNMIGRNVWNASITISGNNPATGPKVRGAWKDKNSA linker (bold SWNVLLDARGALSGIWETGFNLVAFGLSEPSKTTGYN italic)- DAIVLEGSGNFNVNWRVDTEDGNQFHFNSSRDHRGRR monomer CYSCTDNNAFWNWLYANDGRTFQMSFTAY 156 Table 7: Adapter Motifs (a) Alignment of example adapter sequences and consensus sequence and motifs (top line)SNB0016-1 GB(b) Adapter Motif Sequences SEQ Description Sequence ID NO: 157 MAVX1G 158 X2X3VGX4SX4’159 PWVGX4SA 160 TGX5X6WM 161 PX7WMS 162 VGX4SAX9X10X11TGX5163 LRLGX12PFWM Wherein:- X1= any natural amino acid, eg, selected from T, V Q or E; X2=G or P; X3=W or N (preferably W); X4=S, E or W (preferably S); and X4’=A or Y (preferably A); X5=Q or E (preferably Q); X6= any natural amino acid; X7=F, G or C (preferably F); X9= any natural amino acid; X10= any natural amino acid; X11= any natural amino acid; and X12= any natural amino acid (preferably V, R, I or T).

Claims

SNB0016-1 GB CLAIMS:

1. A protein chimaera comprising (i) a polypeptide trimer comprising an interface; (ii) a polypeptide monomer; and (iii) a trimer-to-monomer adapter; wherein the adapter comprises a polypeptide, wherein the adapter polypeptide comprises an interface that is associated with the trimer interface, and wherein the adapter is associated with the protein monomer and the monomer is heterologous to the trimer wherein the chimaera is a non-naturally occurring protein chimaera.

2. The chimaera of claim 1, wherein (i) said interfaces are hydrophobically associated together; and / or (ii) the adapter interface comprises one or more charged amino acids, the trimer interface comprises one or more charged amino acids, and said amino acid(s) of the adapter interface are electrostatically associated with said amino acid(s) of the trimer.

3. The chimaera of claim 1 or 2, wherein each interface has a surface area of at least 800 Å2.

4. The chimaera of any preceding claim, wherein (i) the adapter is heterologous to the trimer; and / or (ii) the adapter is heterologous to the monomer.

5. The chimaera of any preceding claim, wherein the trimer comprises an amino acid sequence that is naturally found in a tailocin or first phage tail fibre or spike and the adapter or monomer comprises an amino acid sequence that is not found in said tailocin or first phage tail fibre or spike.

6. The chimaera of any preceding claim, wherein the protein chimaera is comprised by a transduction particle (optionally a phage), wherein the particle comprises capsid proteins of a Caudoviricetes phage and (i) the monomer is heterologous to said phage; and / or (ii) the particle comprises DNA packaged by said capsid proteins, wherein the DNA is heterologous to said phage.

7. The chimaera of claim 6(ii), wherein the DNA encodes a non-phage protein or RNA, optionally a CRISPR guide RNA or crRNA.SNB0016-1 GB 8. The chimaera of any preceding claim, wherein the protein chimaera is comprised by a transduction particle (optionally a phage) that is capable of infecting a target bacterial or archaeal cell, optionally wherein the particle comprises DNA that encodes (i) an agent that is toxic to the cell; or (ii) a bacterial, archaeal, animal (eg, human), plant or yeast protein.

9. The chimaera of any preceding claim, wherein (a) the monomer comprises a polypeptide of a T-even phage tail fibre (eg, a gp38 polypeptide or fragment thereof); (b) the trimer is heterologous to T-even phages; (c) the monomer comprises a polypeptide of a T2 or T6 phage (eg, a gp38 polypeptide or fragment thereof; or a gp38 variant polypeptide) and the trimer is heterologous to said phage; and / or (d) the adapter is an adapter comprised by a tail fibre of a T-even phage (eg, a T2 or T6 phage) and the monomer is a gp38 polypeptide of said phage or a variant of such a gp38 polypeptide, wherein the T-even phage tail fibre comprises in N- to C-terminal direction a gp37 trimer, said adapter and said gp38 monomer 10. The chimaera of any preceding claim, wherein the trimer comprises a polypeptide fragment of a polypeptide trimer of a virus (eg, phage) or a tailocin tail fibre or spike.

11. The chimaera of any preceding claim, wherein the trimer is associated with a tail fibre base plate polypeptide (eg, a P2 base plate polypeptide).

12. The chimaera of any preceding claim, wherein the chimaera is comprised by (i) a phage or tailocin tail fibre and the tail fibre comprises (in N- to C-terminal direction) said trimer, said adapter and said monomer, wherein the trimer is a trimer of a polypeptide that comprises (in N- to C-terminal direction) a first fragment and a second fragment, wherein the first fragment is heterologous to the second fragment and the second fragment comprises said trimer interface; or (ii) a phage or tailocin spike and the spike comprises (in N- to C-terminal direction) said trimer, said adapter and said monomer, wherein the trimer is a trimer of a polypeptide that comprises (in N- to C-terminal direction) a first fragment and a second fragment, wherein the first fragment is heterologous to the second fragment and the second fragment comprises said trimer interface.SNB0016-1 GB 13. The chimaera of claim 12, wherein (i) the first fragment is heterologous to the adapter; (ii) the first fragment is heterologous to the monomer; (iii) the first fragment is heterologous to the adapter and the monomer; (iv) the chimaera is according to claim 12(i) and the first fragment is a fragment of a polypeptide of a tail fibre of a first phage, and the adapter is comprised by a tail fibre or spike of a second phage, wherein the first and second phage are different types of phage; (v) the chimaera is according to claim 12(ii) and the first fragment is a fragment of a polypeptide of a spike of a first phage, and the adapter is comprised by a tail fibre or spike of a second phage, wherein the first and second phage are different types of phage; (vi) the chimaera is according to claim 12(i) and the first fragment is a fragment of a polypeptide of a tail fibre of a tailocin, and the second fragment is a fragment of a polypeptide of a tail fibre or spike of a second tailocin or a phage, wherein the first and second tailocins are different types of tailocin; or (vii) the chimaera is according to claim 12(ii) and the first fragment is a fragment of a polypeptide of a spike of a tailocin, and the second fragment is a fragment of a polypeptide of a tail fibre or spike of a second tailocin or a phage, wherein the first and second tailocins are different types of tailocin.

14. The chimaera of (i) claim 12 or claim 13 when dependent from claim 12, wherein the second fragment comprises a gp37 trimer-to-monomer interface and the adapter is linked to a gp38 monomer and the adapter comprises a monomer-to-trimer interface that is associated with the gp37 interface; (ii) claim 12 or claim 13 when dependent from claim 12, wherein the second fragment comprises a gp5 trimer-to-monomer interface and the adapter comprises a gp5.4 monomer-to-trimer interface that is associated with the gp5 interface; (iii) claim 12 or claim 13 when dependent from claim 12, wherein the second fragment comprises a bacterial type VI secretion system VgrG protein trimer-to-monomer interface and the adapter comprises a cognate bacterial type VI secretion system PAAR-repeat protein monomer-to-trimer interface that is associated with the VgrG protein interface.

15. The chimaera of (i) Claim 14(i), wherein the gp37 and / or gp38 is a Salmonella phage S16 gp37 and gp38 respectively; orSNB0016-1 GB (ii) Claim 14(ii), wherein the gp5 and / or gp5.4 is a T-even (eg, T2 or T6) phage gp5 and gp5.4 respectively.

16. The chimaera of any preceding claim, wherein (i) the trimer interface is a trimer-to-monomer interface of a trimer of a phage tail or tailocin fibre or spike and the adapter interface is a cognate monomer-to-trimer interface of a monomer of said tail fibre or spike; or (ii) the trimer interface is a trimer-to-monomer interface of a trimer of a bacterial type VI secretion system and the adapter interface is a cognate monomer-to-trimer interface of a monomer of said bacterial type VI secretion system.

17. The chimaera of any preceding claim, wherein the adapter polypeptide is fused to the monomer, optionally via a peptide linker.

18. The chimaera of any preceding claim, wherein the chimaera is comprised by a transduction particle (eg, phage) or tailocin tail fibre or spike and the monomer is at the C-terminus of the tail fibre or spike.

19. The chimaera of any preceding claim, wherein the trimer is a polypeptide homotrimer.

20. The chimaera of any preceding claim, wherein the adapter comprises an alpha-helix polypeptide bundle and the bundle comprises the adapter interface.

21. The chimaera of any preceding claim, wherein the adapter comprises a T-even (eg, T2 or T6) phage tail fibre polypeptide or fragment thereof, optionally linked to a monomer comprising a gp38 polypeptide or a fragment thereof.

22. The chimaera of any preceding claim, wherein the monomer comprises a beta helix and / or a PG II sandwich domain.

23. The chimaera of any preceding claim, wherein the monomer comprises a ligand binding site, optionally at the C-terminus of the chimaeric protein.

24. The chimaera of any preceding claim, wherein the N-terminus of the trimer is associated with a tail fibre or spike of a phage or tailocin base plate.SNB0016-1 GB 25. A tail fibre or spike of a transduction particle (eg, a virus or phage) or a tailocin, the fibre or spike comprising the chimaera of any preceding claim, wherein the fibre or spike comprises (in N- to C-terminal direction) (i) said polypeptide trimer; (ii) said adapter; and (iii) said monomer; wherein the trimer is a trimer of a polypeptide that comprises (in N- to C-terminal direction) a first fragment and a second fragment, wherein the first fragment is heterologous to the second fragment and the second fragment comprises said trimer interface, wherein the first fragment is a first tail fibre or spike protein (or N-terminal fragment thereof).

26. The tail fibre of claim 25, wherein the first and second fragments are respectively fragments of first and second tail fibre proteins (or fragments thereof) of different phage or tailocins, optionally wherein the first fragment is from a Peduovirinae (optionally P2), Muvirus (optionally Mu) or Punavirus (optionally P1) and the second fragment is from a Tevenvirinae (optionally a T2 or T6) phage.

27. The tail fibre or spike of claim 25 or 26, wherein the first fragment is a first tail fibre or spike protein (or N-terminal fragment thereof) that is directly attached to the base plate of a phage or tailocin.

28. The tail fibre or spike of claim 27, wherein the first fragment comprises at least the N-terminal- most 100 (eg, at least the N-terminal-most 150 or 160) consecutive amino acids of the first protein.

29. The tail fibre or spike of claim 27 or 28, wherein the first protein is a phage P2 protein H or homologue thereof of a different phage.

30. The tail fibre or spike of any one of claims 25-29, wherein the second fragment is a fragment of a second tail fibre or spike protein (or C-terminal fragment thereof) and the fragments are joined directly together at a junction; and wherein the amino acid sequence of the first fragment joined to the second fragment comprises a window (W1) of a length (L1) of at least 15 consecutive amino acids, wherein the window comprises the junction and is (i) at least 50% similar or identical to a window (W2) of consecutive amino acids of the first tail fibre or spike protein wherein W2 is an amino acid sequence of length L1; and (ii) at least 50% similar or identical to a window (W3) of consecutive amino acids of the second tail fibre or spike protein wherein W3 is an amino acid sequence of length L1.SNB0016-1 GB 31. The tail fibre or spike of claim 30, wherein (a) the protein chimaera comprises a window (W4) of X consecutive amino acids immediately N- terminal of the junction; (b) the protein chimaera comprises a window (W5) of Y consecutive amino acids immediately C- terminal of the junction; (d) X is at least 4; (e) Y is at least 4; and (f) (i) the amino acid sequence of W4 is at least 50% identical or similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment; and / or (ii) the amino acid sequence of W5 is at least 50% identical or similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment.

32. The tail fibre or spike of claim 31, wherein A: (i) the amino acid sequence of W4 is at least 50% identical or similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment; and (ii) the amino acid sequence of W5 is at least 40% identical or similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment; or B: (i) the amino acid sequence of W4 is at least 40% identical or similar to the C-terminal-most sequence of X consecutive amino acids of the first fragment; and (ii) the amino acid sequence of W5 is at least 50% identical or similar to the N-terminal-most sequence of X consecutive amino acids of the second fragment.

33. The tail fibre or spike of any one of claims 25-32, wherein A: the first fragment is a N-terminal fragment of a tail fibre of a tailocin or a phage that is not a T-even phage; and B: the adapter comprises a polypeptide (or fragment thereof) of a T-even phage and / or the monomer comprises a polypeptide (or fragment thereof) of a T-even phage.

34. The tail fibre or spike of any one of claims 25-33, wherein A: the first fragment is a N-terminal fragment of a tail fibre of a tailocin or a phage that is not a T-even phage; and B: the trimer comprises a polypeptide (or fragment thereof, optionally the secondSNB0016-1 GB fragment) of a T-even phage.

35. The chimaera, tail fibre or spike of any preceding claim, wherein the trimer comprises a gp37 polypeptide (or fragment thereof) and / or the adapter comprises a gp38 polypeptide (or fragment thereof).

36. The chimaera, tail fibre or spike of any preceding claim, wherein the C-terminus of each polypeptide of the trimer comprises a C-terminal fragment of a gp37 polypeptide; optionally, wherein the fragment is devoid of at least the first 50, 100, 110, 120 or 130 residues of the gp37; optionally, wherein the fragment is devoid of a sequence consisting of residues 1-135 of the gp37.

37. The chimaera, tail fibre or spike of any preceding claim, wherein the C-terminus of each polypeptide of the trimer comprises a gp37 polypeptide (or fragment thereof) that is fused at its N-terminus to a heterologous tail fibre or spike polypeptide.

38. The chimaera, tail fibre or spike of any preceding claim, wherein each polypeptide of the trimer comprises (i) a polypeptide (or fragment thereof) of a first tail fibre that is fused to (ii) a polypeptide (or fragment thereof) of a second tail fibre, wherein the tail fibres are different.

39. The chimaera, tail fibre or spike of claim 38, wherein the tail fibres are tail fibres of (i) a virus (eg, a phage) and a tailocin; or (ii) different viruses (eg, different phages).

40. The chimaera, tail fibre or spike of claim 39, wherein the second tail fibre is a tail fibre of a T- even (eg, T2 or T6) phage and the first tail fibre is a tail fibre of a phage that is not a T-even phage.

41. The chimaera, tail fibre or spike of any one of claims 38-40, wherein the first tail fibre is a tail fibre of a tailocin, lambda phage, a Peduovirinae (optionally P2), a Muvirus (optionally Mu), or Punavirus (optionally P1) and optionally the second tail fibre is a tail fibre of a Tevenvirinae phage (optionally a T2 or T6).

42. A virus (eg, a phage) comprising the chimaera, tail fibre or spike of any preceding claim; or a tailocin comprising the chimaera, tail fibre or spike of any preceding claim.

43. A library of tail fibres or spikes, wherein each tail fibre or spike is according to any one of claims 25-41 or comprised by a virus of claim 42, wherein the monomers of at least some of theSNB0016-1 GB members of the library differ from each other.

44. A library comprising a plurality of adapter-monomers, wherein each adapter is an adapter as defined in preceding claim and associated with a polypeptide monomer, wherein each adapter- monomer comprises the adapter then the monomer in N- to C-terminal direction, wherein the monomers of at least some of the adapter-monomer members of the library differ from each other, optionally wherein each adapter comprises an N-terminal interface that is associated with a polypeptide trimer interface.

45. The library of claim 44, wherein each said adapter is fused to a capsid protein of a virus, wherein the virus comprises a tail fibre comprising (in N- to C-terminal direction) said capsid protein, the adapter and the monomer.

46. A library comprising a plurality of polypeptide monomers, wherein the monomers differ from each other (optionally wherein the monomers are variants of a parental monomer and differ from each other by one or more amino acid residues), wherein each said monomer is fused to a protein displayed by a carrier (eg, a virus (such as a phage), cell or nanoparticle).

47. The library of any one of claims 43-46, wherein C-terminal peptide loops of monomers of at least some of the members of the library differ from each other.

48. The library of any one of claims 43-47, wherein different members of the library comprise different monomers wherein the monomers are ligand binding sites, the ligand binding sites differing between said members.

49. A phage display library, wherein the library is according to any one of claims 43-48.

50. A method of selecting a tail fibre or spike sequence, the method comprising contacting a library according to claim 43, 44 or 46, or any one of claims 45 and 47-49 when dependent from claim 43, 44 or 46 with a ligand, wherein the tail fibres are displayed on carriers, wherein each carrier comprises a respective nucleic acid encoding the tail fibre or spike that it displays, wherein monomers of tail fibres or spikes of the library bind to the ligand, the method comprising isolating nucleic acid of a carrier whose fibre or spike monomer bound to the ligand; and determining the nucleotide sequence of the monomer of said fibre or spike and / or isolating said fibre or spike.

51. The method of claim 50, wherein each carrier is a virus (eg, a phage), cell or nanoparticle.SNB0016-1 GB 52. A method of producing a tail fibre or spike, the method comprising (i) providing a protein expression construct, wherein the construct comprises a nucleic acid that encodes a phage tail fibre or spike, the nucleic acid comprising said nucleotide sequence determined by the method of claim 50 or 51; (ii) expressing the tail fibre or spike encoded by the construct; and (iii) optionally isolating the tail fibre or spike.

53. A method of producing a tail fibre or spike, the method comprising (i) contacting a library according to claim 43, 44 or 46, or any one of claims 45 and 47-49 when dependent from claim 43, 44 or 46 with a ligand, wherein the monomers are displayed on carriers, wherein each carrier comprises a respective nucleic acid encoding the monomer that it displays, wherein monomers of the library bind to the ligand; (ii) isolating nucleic acid of a carrier whose monomer bound to the ligand; and (iii) determining the nucleotide sequence of the monomer of step (ii); the method further comprising (iv) providing a protein expression construct, wherein the construct comprises a nucleic acid that encodes a phage tail or tailocin fibre or spike, the nucleic acid comprising said nucleotide sequence determined in step (iii) or a nucleotide sequence that differs by no more than 5 codon changes; (v) expressing tail fibre or spike encoded by the construct; and (vi) optionally isolating tail fibre or spike.

54. The method of claim 52 or 53, wherein the construct is a plasmid (optionally comprised by a bacterium) or a DNA comprised by the genome of a host bacterium.

55. The method of claim 54, wherein the DNA encodes a phage, tailocin or transduction particle when expressed in a host bacterial cell and said step of expressing the tail fibre or spike comprises producing the phage, tailocin or particle in the bacterium; optionally wherein the method comprises isolating the phage, tailocin or particle.

56. The method of claim 55, further comprising formulating the phage, tailocin or particle with a pharmaceutically acceptable diluent, carrier or excipient, thereby producing a pharmaceutical composition.

57. The chimaera, chimaera, tail fibre, spike, tailocin, virus, library or method of any preceding claim, whereinSNB0016-1 GB (i) the chimaera comprises immediately N-terminal to the junction an amino acid sequence selected from SEQ ID NOs: 24-41 or an amino acid sequence that is at least 70% identical to said selected sequence, (ii) the chimaera comprises immediately C-terminal to the junction an amino acid sequence selected from SEQ ID NOs: 42-59 or an amino acid sequence that is at least 70% identical to said selected sequence, or (iii) the chimaera herein comprises an amino acid sequence selected from SEQ ID NOs: 60-77 and 192 or an amino acid sequence that is at least 70% identical to said selected sequence.

58. The chimaera, chimaera, tail fibre, spike, tailocin, virus, library or method of any preceding claim, wherein (i) the adapter comprises an amino acid sequence selected from SEQ ID NOs: 79-85; or a sequence that is at least 70% identical to said selected sequence; (ii) the adapter comprises a motif sequence selected from SEQ ID NOs: 157-163; (iii) the monomer herein comprises an amino acid sequence selected from SEQ ID NOs: 143- 149; or a sequence that is at least 70% identical to said selected sequence; (iv) the linker comprises an amino acid sequence selected from SEQ ID NOs: 86-142; or a sequence that is at least 70% identical to said selected sequence; and / or (v) the adapter, linker and monomer (in N- to C-terminal direction) comprises an amino acid sequence selected from SEQ ID NOs: 150-156; or a sequence that is at least 70% identical to said selected sequence.

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