GROWTH, SURVIVAL AND CHARACTERIZATION OF CSPA IN SALMONELLA-ENTERITIDIS FOLLOWING COLD SHOCK

Salmonella enteritidis is a major foodborne microbial pathogen that ca n grow and survive at low temperatures for a considerable period of ti me. Increased survival was evidenced from a frozen S. enteritidis cult ure when treated at 10 degrees C prior to freezing. Western blot analy sis with Escherichia coli CspA antibody and analysis of radiolabeled p roteins 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 sh ock protein, CS7.4, similar in size to that reported for E. coli. Clon ing 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 ope n reading frame (ORF) with the E. coli cspA gene. However, the differe nces in the nucleotide sequences between E. coli and S. enteritidis cs pA genes in the putative repressor protein binding domain, the fragmen t 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 protecti ng S. enteritidis from the damaging effects of cold or freezing temper atures is not yet understood.