Periplasmic peptidyl-prolyl isomerases SurA and FkpA play an important role in the starvation-stress response (SSR) of Salmonella enterica serovar Typhimurium.
Carbon-energy source (C)-starved cells of Salmonella enterica serovar Typhimurium (S. Typhimurium) are remarkably more resistant to stress than actively growing ones. Carbon-starved S. Typhimurium is capable of withstanding extended periods of starvation and assault from a number of different stresses that rapidly kill growing cells. These unique properties of the C-starved cell are the direct result of a series of genetic and physiological adaptations referred to as the starvation-stress response (SSR). Previous work established that the SSR of S. Typhimurium is partially regulated by the extracytoplasmic function sigma factor sigma(E). As part of an effort to identify sigma(E)-regulated SSR genes, we investigated surA and fkpA, encoding two different classes of peptidyl-prolyl isomerase that function in folding cell envelope proteins. Both surA and fkpA are members of the heat-shock-inducible sigma(E) regulon of Escherichia coli. Although both genes are expressed in C-starved Salmonella cells, evidence indicates that surA and fkpA are not C-starvation-inducible. Furthermore, their expression during C-starvation does not appear to be sigma(E)-dependent. Nonetheless, surA and fkpA proved to be important, to differing degrees, for long-term C-starvation survival and for the cross-resistance of C-starved cells to high temperature, acidic pH, and the antimicrobial peptide polymyxin B, but neither were required for cross-resistance to oxidative stress. These results point to fundamental differences between heat-shock-inducible and C-starvation-inducible genes regulated by sigma(E) and suggest that genes other than surA and fkpA are involved in the sigma(E)-regulated branch of the SSR in Salmonella.
Department of Biology, University of West Georgia, Carrollton, GA 30118, USA. wkenyon@westga.edu
William J
WJ
Kenyon
Sue
S
Humphreys
Mark
M
Roberts
Michael P
MP
Spector
D000143:Acids / Q000633:toxicity; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006358:Hot Temperature; D019696:Peptidylprolyl Isomerase / Q000378:metabolism*; D011112:Polymyxin B / Q000494:pharmacology; D018085:Regulon; D012486:Salmonella typhimurium / Q000187:drug effects / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D012808:Sigma Factor / Q000378:metabolism; D013312:Stress, Physiological
D000143:Acids; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D012808:Sigma Factor; C063202:sporulation-specific sigma factors; D002244:Carbon; D019696:Peptidylprolyl Isomerase; D011112:Polymyxin B