Abstract：In order to study the effect of deletion of crp (cAMP receptor protein) gene and insertion of gfp (green fluorescence protein) gene to the virulence and immunogenicity of Salmonella choleraesuis attenuated vaccine C500 strain, and to constuct crp-deleted C500 as a carrier of multip oral vaccine, crp-/gfp+mutant of deletion of crp and insertion of gfp was constructed. Firstly, the recombination suicide vector with 320 bp-deleted crp gene and 720 bp-insert gfp gene was constructed and conjugated with C500. The unmarked crp deleted ang gfp inserted strain was selected by two-step method. crp deletion and gfp insertion on the genome was determined by PCR and fluorescence microscope. In conclusion, the crp-/gfp+mutant was successfully constructed.
