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Compensatory role of PspA, a member of the phage shock protein operon, in rpoE mutant Salmonella enterica serovar Typhimurium
Author(s) -
Becker Lynne A.,
Bang IelSoo,
Crouch MarieLaure,
Fang Ferric C.
Publication year - 2005
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04604.x
Subject(s) - regulon , salmonella enterica , biology , operon , sigma factor , mutant , microbiology and biotechnology , salmonella , rpos , virulence , gene expression , bacteria , gene , genetics , promoter
Summary σ E is an alternative sigma factor that responds to and ameliorates extracytoplasmic stress. In Salmonella enterica serovar Typhimurium ( S. Typhimurium), σ E is required for oxidative stress resistance, stationary‐phase survival and virulence in mice. Microarray analysis of stationary‐phase gene expression in rpoE mutant bacteria revealed a dramatic increase in expression of pspA , a member of the phage shock protein ( psp ) operon. The psp operon can be induced by filamentous bacteriophages or by perturbations of protein secretion, and is believed to facilitate the maintenance of proton motive force (PMF). We hypothesized that increased pspA expression may represent a compensatory response to the loss of σ E function. Increased pspA expression was confirmed in rpoE mutant Salmonella and also observed in a mutant lacking the F 1 F 0 ATPase. Alternatively, expression of pspA could be induced by exposure to CCCP, a protonophore that disrupts PMF. An rpoE pspA double mutant strain was found to have a stationary‐phase survival defect more pronounced than that of isogenic strains harbouring single mutations. The double mutant strains were also more susceptible to killing by CCCP or by a bactericidal/permeability‐increasing protein (BPI)‐derived anti‐microbial peptide. Using fluorescence ratio imaging, differences were observed in the Δψ of wild‐type and rpoE or pspA mutant bacteria. These findings suggest that pspA expression in S. Typhimurium is induced by alterations in PMF and a functional σ E regulon is essential for the maintenance of PMF.