“
“Listeria monocytogenes is a food-borne pathogen that can survive

under a wide range of environmental and energy stress conditions. The general stress response controlled by σB largely contributes to stress resistance in L. monocytogenes. Moreover, the bacterial cell wall is the first defense PLX4032 molecular weight against cellular stress and as such is the target of numerous antibiotics. We therefore hypothesize that σB contributes to monitoring the integrity of cell walls. We evaluated σB activity in wild type and ΔsigB mutant L. monocytogenes containing reporter fusions (σB-dependent opuCA promoter and a lacZ reporter gene) during the early exponential growth phase by measuring the specific activity of β-galactosidase after vancomycin (2 μg mL−1 final concentration) stress. σB activity is significantly induced only in the wild-type strain by addition of vancomycin. In

addition, we identified σB-dependent vancomycin-inducible proteins using LC-ESI-MS/MS analysis. Two independent proteomic analyses confirmed the minimum twofold upregulation of 18 vancomycin-inducible σB-dependent stress response proteins in the wild-type strain compared with the ΔsigB mutant. The functions PD0332991 purchase of these proteins are associated with cell wall biogenesis, intracellular transport, general stress response, cell metabolism and virulence. These results suggest that the σB protein may contribute to the monitoring of cell wall integrity. Listeria monocytogenes is a widely distributed intracellular pathogen that causes listeriosis, a serious illness from which children, pregnant

women and immunocompromised individuals are at risk. Infection is most often caused by the ingestion of contaminated foods, such as those most frequently associated with raw milk, soft cheeses, raw vegetables and refrigerated ready-to-eat products (Farber & Peterkin, 1991). Listeria monocytogenes has the ability to grow in very diverse environments; it can survive in a wide temperature range (−1 to 45 °C), a broad pH range (4.5–9.0) and in high salt concentrations (10% NaCl) (Cole et al., 1990; Sleator et al., 2001). These unique resistance properties are related to the general stress response, which is controlled by the Resveratrol alternative sigma factor σB (Wiedmann et al., 1998; O’Byrne & Karatzas, 2008). Listeria monocytogenesσB was found to play a role in the general stress response. σB-null mutants demonstrate increased sensitivity under salt, acid, cold, heat, ethanol and oxidative stress, as well as carbon starvation (Becker et al., 1998, 2000; Wiedmann et al., 1998). About 150 σB-dependent genes are known to be expressed under stress conditions, where they contribute to stress resistance in L. monocytogenes (Raengpradub et al., 2008).