Abstract:In order to study the adaptive evolution mechanism of L. casei Zhang in antibiotic environment, the gene knockout system was constructed and the resistant phenotype of mutants was studied. The homologous arm sequence of the XRE family transcriptional regulator gene was amplified by PCR, and a knockout vector with internal deletion of LCAZH_0458 gene was constructed.Using the Cre/lox gene recombination system, the double-crossing L. casei Zhang-G/A-1200/600-0458:: lox66-P32-cat-lox71 was screened and the mutant strain L. casei Zhang-G/A-1200/600-Δ0458 was constructed. Besides, the antibiotic resistance phenotype of the wild strain and mutants were studied by the dilution method. The drug-resistant phenotypic results showed that the turbidity was increased by a factor of about 2 when the gentamicin concentrations were 8 μg/mL and 16 μg/mL compared to the wild strain. In the amoxicillin environment, there was no change in the turbidity and viable counts. LCAZH_0458 has a certain regulatory effect on the gentamicin environment of L. casei.
