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The alternative sigma factor σ E is required for resistance of Salmonella enterica serovar Typhimurium to anti‐microbial peptides
Author(s) -
Crouch MarieLaure,
Becker Lynne A.,
Bang IelSoo,
Tanabe Hiroki,
Ouellette Andre J.,
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.1365-2958.2005.04578.x
Subject(s) - salmonella enterica , sigma factor , biology , formate dehydrogenase , microbiology and biotechnology , salmonella , cell envelope , bacterial cell structure , virulence factor , bacterial outer membrane , bacteria , enterobacteriaceae , virulence , pathogen , biochemistry , escherichia coli , gene , enzyme , cofactor , genetics , rna polymerase
Summary The enteric pathogen Salmonella enterica serovar Typhimurium ( S. Typhimurium) encounters a variety of anti‐microbial peptides during the course of infection. We report here that the extracytoplasmic sigma factor σ E (RpoE) is required for Salmonella resistance to killing by the bactericidal/permeability‐increasing protein (BPI)‐derived peptide P2 and the murine α‐defensin cryptdin‐4 (Crp4). Moreover, σ E ‐deficient S. Typhimurium is attenuated for virulence after oral infection of immunocompromised gp91 phox –/– mice that lack a functional NADPH phagocyte oxidase, suggesting that σ E plays an important role in resistance to non‐oxidative mucosal host defences such as anti‐microbial peptides. Although both P2 and Crp4 target the cell envelope, bacterial killing by these peptides appears to occur by distinct mechanisms. Formate enhances bacterial resistance to P2, as previously demonstrated, but not to Crp4. Both σ E and cytoplasmic membrane‐associated formate dehydrogenase are required for the protective effect of formate against P2. In contrast to P2, Crp4 does not inhibit bacterial respiration at lethal concentrations. However, both peptides induce expression of rpoE , suggesting that they trigger a common mechanism for sensing extracytoplasmic stress.