This invention discloses a method for
directed evolution of antibiotic-resistant
Escherichia coli strains based on
cytidine deaminase, belonging to the field of microbial
directed evolution and
genetic engineering technology. This method uses E. coli as the host, introducing a recombinant
plasmid expressing an optimized double-stranded
cytidine deaminase
mutant. Utilizing the
low toxicity and high mutagenicity of this
mutant, continuous passage evolution is carried out under gradient concentrations of
aminoglycoside antibiotics (
kanamycin and
streptomycin). Combined with whole-
genome sequencing, molecular docking, and
reverse genetics verification, the A145T
missense mutation in the wcaE
gene is identified as the core functional site. This invention overcomes the shortcomings of traditional spontaneous and chemical
mutagenesis, which suffer from low efficiency and significant strain damage. The
mutation type is controllable, the evolutionary cycle is short, and the obtained engineered strains can tolerate up to 300 mg / L
kanamycin while exhibiting
streptomycin cross-resistance, and the
genetic stability of the tolerance trait is strong. This method is simple, highly reproducible, and suitable for industrial breeding of stress-resistant E. coli, and can be widely applied in antibiotic
fermentation, industrial microbial culture, and other scenarios.