title: Contribution of the hdeB-like gene (SEN1493) to survival of Salmonella enterica enteritidis Nal(R) at pH 2.
abstract: Periplasmic proteins are particularly vulnerable to denaturation upon entry into a highly acid environment. In Escherichia coli, a level of protection of these proteins is afforded by acid-inducible chaperonins encoded by hdeAB. In contrast, Salmonella enterica only harbors an hdeB-like gene and it is currently not known what function it plays in this genus. In the present study, the hdeB-like gene was deleted in Salmonella enterica Enteritidis Nal(R) and Salmonella enterica Kentucky 3795. When grown overnight in tryptic soy broth (TSB) medium buffered at pH 5.5 and then exposed to TSB pH 2 for 20 min, Enteritidis wild-type strain experienced a 0.5-log10 reduction in colony-forming units, whereas the deletion strain's surviving cells were reduced by 1.6 log10. No difference in survival was observed in the corresponding Salmonella enterica Kentucky 3795 strains treated the same way. Exposure of the strains to pH 2.5 or 3 resulted in the same log reduction regardless of the presence of the hdeB-like gene. When wild-type and deletion strains of both serovars were grown in medium buffered at pH 7 prior to exposure to the acidic pHs, no difference in survival with respect to serovar or presence/absence of the hdeB-like gene was found. Salmonella enterica Enteritidis Nal(R) carrying its own or the intragenic region upstream of the hdeB-like from Salmonella enterica Kentucky 3795 cloned in front of the gfp gene from pFPV25 showed maximum fluorescence when grown at pH 5.5, whereas the corresponding plasmid-carrying Salmonella enterica Kentucky strains did not exhibit fluorescence regardless of the pH of the growth medium. Therefore, the hdeB-like gene in Salmonella enterica Enteritidis, but not in Salmonella enterica Kentucky 3795, contributed to survival at pH 2 and its expression is responsive to the pH of the medium.
authors: Department of Animal and Food Sciences, University of Delaware , Newark, Delaware.
authors: Rolf D
authors: RD
authors: Joerger
authors: Steven
authors: S
authors: Choi
mesh_terms: D000143:Acids / Q000737:chemistry*; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry; D005798:Genes, Bacterial; D006863:Hydrogen-Ion Concentration; D019779:Salmonella enterica / Q000235:genetics*; D012477:Salmonella enteritidis / Q000235:genetics*
chemical_list: D000143:Acids; D003470:Culture Media