Objective To investigate the effect of acetyltransferase/deacetylase Pat/CobB on the acid tolerance response (ATR) of Salmonella typhimurium. Methods The pat gene and cobB gene of Salmonella Typhimurium, which encode acetyltransferase and deacetylase, were deleted by the λ-Red system. The growth differences were compared through the growth curves. The transcriptional levels of some genes involved in acid stress were detected by Real-Time PCR. The differences of acid tolerance response between deletion mutants and wild type strains both at the log phase and at the stationary phase were examined by the colony forming units (Cfu) counting. Results The deletion mutants of pat and cobB of Salmonella typhimurium were successfully constructed. The deletion of pat and cobB did not affect the growth of Salmonella Typhimurium and the acid tolerance response both at the log phase and at the stationary phase. Conclusion The pat/cob genes of Salmonella Typhimurium encode the acetylase/deacetylase. The mutation of pat/cob genes will not affect the growth of bacteria and will not involve in the acid tolerance response.