Cupriavidus Plasmid Stabilization via Par System
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Solution Overview
Problem
Recombinant plasmid vectors used in bacteria such as Cupriavidus necator for polyhydroxyalkanoate production are unstable, leading to plasmid elimination during bacterial proliferation, and existing stabilization methods rely on antibiotic selective pressure, which is undesirable for commercial production.
Innovation Solution
A recombinant vector is developed with an origin of replication specific to Cupriavidus necator and incorporating the par system from megaplasmid pMOL28, eliminating the need for antibiotic selective pressure and preventing conjugative transfer, thereby stabilizing the plasmid within the bacteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If broad-host-range plasmid vectors (pJRD215-derived or pBBR-derived) are used for gene transfer into Cupriavidus necator, then the vectors can be transferred into a wide range of hosts, but the plasmid stability decreases significantly when polyhydroxyalkanoates accumulate in the cells
Solution Approach 1:
The plasmid vector is segmented into functional modules: a Cupriavidus necator-specific origin of replication (oriRne) for host-specific replication control, a par system from pMOL28 for active partitioning and stability, and removable antibiotic resistance markers. This segmentation allows optimization of each function independently, achieving both host adaptability and plasmid stability in PHA-producing strains.
2Stability of the object's composition
If antibiotic-due selective pressure is applied to stabilize plasmid retention, then plasmid retention is maintained, but production costs increase and environmental risks arise
Solution Approach 1:
The plasmid vector employs a self-service mechanism through the par system (parA28, parB28, parS) that actively partitions plasmid copies to daughter cells during cell division. This self-stabilization mechanism maintains plasmid retention without requiring external antibiotic selection pressure, eliminating continuous production costs and environmental risks associated with antibiotic use.
3Stability of the object's composition
If antibiotic-due selective pressure is applied during cultivation, then plasmid retention is stabilized, but the amount of antibiotic required significantly increases production cost
Solution Approach 1:
The par system provides self-service plasmid stabilization through active partitioning mechanisms that ensure each daughter cell receives at least one plasmid copy during cell division. This eliminates the need for continuous antibiotic addition, reducing antibiotic consumption to zero during the production phase while maintaining high plasmid retention rates.
4Stability of the object's composition
If the par system from pMOL28 is incorporated into the recombinant vector, then plasmid stability is improved without antibiotic pressure, but the vector design complexity increases
Solution Approach 1:
The par system from pMOL28 is designed as a universal, modular component that can be integrated into various plasmid backbones. The parA28, parB28, and parS elements function as a standardized stability module that works across different vector designs, reducing overall system complexity through component standardization and enabling easy adaptation to different gene expression needs.
Data Source
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AI summary
It is an object of the present invention to develop a novel vector. Preferably, the object is to develop a novel vector which can be stably retained in bacteria of the genus Ralstonia, Cupriavidus or Wautersia without any antibiotic-due selective pressure and has no transferability by conjugation. Another object is to provide a strain which can stably produce polyhydroxyalkanoate using the vector, and a method for producing a polyhydroxyalkanoate using the strain. The present invention provides a novel recombinant vector which contains an origin of DNA replication functioning in bacteria of the genus Ralstonia, Cupriavidus or Wautersia. Particularly, the transformant, which is obtained by using a recombinant vector which contains the origin of DNA replication functioning in bacteria of the genus Ralstonia, Cupriavidus or Wautersia and contains a region for a recombinant vector stabilization (par region) can make the vector to be stably retained in bacteria, and can efficiently produce a polyhydroxyalkanoate.