title: Effects of growth phase and temperature on σB activity within a Listeria monocytogenes population: evidence for RsbV-independent activation of σB at refrigeration temperatures.
abstract: The alternative sigma factor σB of Listeria monocytogenes is responsible for regulating the transcription of many of the genes necessary for adaptation to both food-related stresses and to conditions found within the gastrointestinal tract of the host. The present study sought to investigate the influence of growth phase and temperature on the activation of σB within populations of L. monocytogenes EGD-e wild-type, ΔsigB, and ΔrsbV throughout growth at both 4°C and 37°C, using a reporter fusion that couples expression of EGFP to the strongly σB-dependent promoter of lmo2230. A similar σB activation pattern within the population was observed in wt-egfp at both temperatures, with the highest induction of σB occurring in the early exponential phase of growth when the fluorescent population rapidly increased, eventually reaching the maximum in early stationary phase. Interestingly, induction of σB activity was heterogeneous, with only a proportion of the cells in the wt-egfp population being fluorescent above the background autofluorescence level. Moreover, significant RsbV-independent activation of σB was observed during growth at 4°C. This result suggests that an alternative route to σB activation exists in the absence of RsbV, a finding that is not explained by the current model for σB regulation.
authors.affiliation: Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Ireland.
authors.forename: Marta
authors.initials: M
authors.lastname: Utratna
authors.affiliation: Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Ireland ; Waters Corporation, Milford, MA 01757, USA.
authors.forename: Eoin
authors.initials: E
authors.lastname: Cosgrave
authors.affiliation: Regenerative Medicine Institute (REMEDI), National Centre for Biomedical Engineering Science, National University of Ireland, University Road, Galway, Ireland.
authors.forename: Claas
authors.initials: C
authors.lastname: Baustian
authors.affiliation: Regenerative Medicine Institute (REMEDI), National Centre for Biomedical Engineering Science, National University of Ireland, University Road, Galway, Ireland.
authors.forename: Rhodri H
authors.initials: RH
authors.lastname: Ceredig
authors.affiliation: Bacterial Stress Response Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Ireland.
authors.forename: Conor P
authors.initials: CP
authors.lastname: O'Byrne
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D003080:Cold Temperature; D017931:DNA Primers; D005434:Flow Cytometry; D005456:Fluorescent Dyes; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008089:Listeria monocytogenes / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D010957:Plasmids / Q000378:metabolism; D012808:Sigma Factor / Q000378:metabolism*; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D005456:Fluorescent Dyes; C086522:RsbV protein, Bacteria; C079011:SigB protein, Bacteria; D012808:Sigma Factor; D049452:Green Fluorescent Proteins
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