@article{mbs:/content/journal/micro/10.1099/mic.0.27257-0, author = "Sue, David and Fink, Daniel and Wiedmann, Martin and Boor, Kathryn J.", title = "σB-dependent gene induction and expression in Listeria monocytogenes during osmotic and acid stress conditions simulating the intestinal environment", journal= "Microbiology", year = "2004", volume = "150", number = "11", pages = "3843-3855", doi = "https://doi.org/10.1099/mic.0.27257-0", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.27257-0", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", keywords = "qRT-PCR, quantitative RT-PCR", abstract = " Listeria monocytogenes must overcome a variety of stress conditions in the host digestive tract to cause foodborne infections. The alternative sigma factor σ B, encoded by sigB, is responsible for regulating transcription of several L. monocytogenes virulence and stress-response genes, including genes that contribute to establishment of gastrointestinal infections. A quantitative RT-PCR assay was used to measure mRNA transcript accumulation for the virulence genes inlA and bsh, the stress-response genes opuCA and lmo0669 (encoding a carnitine transporter and an oxidoreductase, respectively) and the housekeeping gene rpoB. Assays were conducted on mid-exponential phase L. monocytogenes cells exposed to conditions reflecting osmotic (0·3 M NaCl) or acid (pH 4·5) conditions typical for the human intestinal lumen. In exponential-phase cells, as well as under osmotic and acid stress, inlA, opuCA and bsh showed significantly lower absolute expression levels in a L. monocytogenes ΔsigB null mutant compared to wild-type. A statistical model that normalized target gene expression relative to rpoB showed that accumulation of inlA, opuCA and bsh transcripts was significantly increased in the wild-type strain within 5 min of acid and osmotic stress exposure; lmo0669 transcript accumulation increased significantly only after acid exposure. It was concluded that σ B is essential for rapid induction of the tested stress-response and virulence genes under conditions typically encountered during gastrointestinal passage. As inlA, bsh and opuCA are critical for gastrointestinal infections in animal models, the data also suggest that σ B contributes to the ability of L. monocytogenes to cause foodborne infections.", }