Whether within the host or in the external environment, enteric bacteria often survive under conditions that do not support exponential growth. One factor frequently preventing growth is starvation for a carbon and energy source (C-starvation). Upon encountering such conditions, Salmonella enterica serovar Typhimurium (S. Typhimurium) undergoes a series of changes in global gene expression and physiology that we refer to is the Starvation-Stress Response (SSR). The SSR results in a cell that is capable of surviving continued, long-term starvation and exposure to a variety of other stresses. Previously, we discovered that the SSR is partially regulated by the alternate sigma factor, sigma(E), encoded by the rpoE gene. We showed that sigma(E) is activated and accumulates during C-starvation and that rpoE is essential for long-term C-starvation survival and for C-starvation-induced cross-resistances. Sigma(E)-type sigma factors control the expression of extra-cytoplasmic functions. However, the genes regulated by such sigma factors varies greatly depending upon the bacterial species. Our preliminary data indicates that the set of genes regulated by sigma(E) during C-starvation in S. Typhimurium is very different from the rpoE-regulon of E. coli reported in the literature. Therefore, our first goal is to identify S. Typhimurium genes induced in response to C-starvation in a sigma(E)-dependent manner. A few of the more interesting genes (e.g., genes unique to Salmonella) will be chosen for further characterization. Using knock-out mutants, we will determine the role of each gene in long-term C-starvation survival and in C-starvation-induced cross-resistance to high temperature, low pH, oxidizing agents, and antimicrobial compounds. In addition, we will further investigate the regulation of these genes by other known stress response regulators such as cAMP-CRP, ppGpp, sigma(S), Lrp, OxyR, SoxRS, Fnr, ArcAB, PhoPQ, and PmrAB. Through our collaboration with Dr. Mark Roberts (Univ. of Glasgow), we will determine the role of these sigma(E)-SSR genes in mouse virulence.
| Kenyon, William J; Humphreys, Sue; Roberts, Mark et al. (2010) Periplasmic peptidyl-prolyl isomerases SurA and FkpA play an important role in the starvation-stress response (SSR) of Salmonella enterica serovar Typhimurium. Antonie Van Leeuwenhoek 98:51-63 |
| Kenyon, William J; Thomas, Sheena M; Johnson, Erin et al. (2005) Shifts from glucose to certain secondary carbon-sources result in activation of the extracytoplasmic function sigma factor sigmaE in Salmonella enterica serovar Typhimurium. Microbiology 151:2373-83 |
| Rich, S M; Sawyer, S A; Barbour, A G (2001) Antigen polymorphism in Borrelia hermsii, a clonal pathogenic bacterium. Proc Natl Acad Sci U S A 98:15038-43 |
