| Temporal transcriptomic analysis of the Listeria monocytogenesEGD-e σBregulon (2008) | |||||||||||
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| Abstract Background The opportunistic food-borne gram-positive pathogen Listeria monocytogenes can exist as a free-living microorganism in the environment and grow in the cytoplasm of vertebrate and invertebrate cells following infection. The general stress response, controlled by the alternative sigma factor, σ B , has an important role for bacterial survival both in the environment and during infection. We used quantitative real-time PCR analysis and immuno-blot analysis to examine σ B expression during growth of L. monocytogenes EGD-e. Whole genome-based transcriptional profiling was used to identify σ B -dependent genes at different growth phases. Results We detected 105 σ B -positively regulated genes and 111 genes which appeared to be under negative control of σ B and validated 36 σ B -positively regulated genes in vivo using a reporter gene fusion system. Conclusion Genes comprising the σ B regulon encode solute transporters, novel cell-wall proteins, universal stress proteins, transcriptional regulators and include those involved in osmoregulation, carbon metabolism, ribosome- and envelope-function, as well as virulence and niche-specific survival genes such as those involved in bile resistance and exclusion. Ten of the σ B -positively regulated genes of L. monocytogenes are absent in L. innocua . A total of 75 σ B -positively regulated listerial genes had homologs in B. subtilis , but only 33 have been previously described as being σ B -regulated in B. subtilis even though both species share a highly conserved σ B -dependent consensus sequence. A low overlap of genes may reflects adaptation of these bacteria to their respective environmental conditions. | |||||||||||
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