Growth, survival and characterization of cspA in Salmonella enteritidis following cold shock.

Abstract

Salmonella enteritidis is a major foodborne microbial pathogen that can grow and survive at low temperatures for a considerable period of time. Increased survival was evidenced from a frozen S. enteritidis culture when treated at 10 degrees C prior to freezing. Western blot analysis with Escherichia coli CspA antibody and analysis of radiolabeled proteins from S. enteritidis cultures after cold shock at 10 degrees C and 5 degrees C showed increased expression of a 7.4-kDa major cold shock protein, CS7.4, similar in size to that reported for E. coli. Cloning followed by nucleotide sequence analysis of the cspA gene from S. enteritidis showed a 100% nucleotide sequence identity in the promoter elements (-35 and -10) and the amino acid sequence encoded by the open reading frame (ORF) with the E. coli cspA gene. However, the differences in the nucleotide sequences between E. coli and S. enteritidis cspA genes in the putative repressor protein binding domain, the fragment 7, and in various segments throughout the upstream 0.642-kbp DNA may contribute to the expression of CS7.4 at less stringent temperatures in S. enteritidis. As in E. coli, the actual role of CS7.4 in protecting S. enteritidis from the damaging effects of cold or freezing temperatures is not yet understood.