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dc.contributor.advisorO'Byrne, Conor P.
dc.contributor.authorO'Donoghue, Beth
dc.date.accessioned2017-02-15T14:58:51Z
dc.date.issued2016-11-30
dc.identifier.urihttp://hdl.handle.net/10379/6310
dc.description.abstractThe alternative sigma factor σB is conserved across several Gram-positive bacteria species as the major general stress response (GSR) regulator. For the food-borne pathogen Listeria monocytogenes, σB enables the bacterium to persist in growth-limiting environments, thus posing a serious concern for food processing industries. Activation of σB is dependent on signalling from a multiprotein stress-sensing complex known as the stressosome. Here, we investigate the individual roles of the five identified stress sensor proteins: RsbR, the blue-light photoreceptor Lmo0799, Lmo0161, Lmo1642 and Lmo1842 which are thought to form a multi-protein stressosome complex. Mutant strains were constructed or obtained, each lacking RsbR or one of its-paralogues and were subjected to a number of phenotypic tests. Blue (460-470 nm) light was found to have a clear inhibitory effect on growth. Removal of the Lmo0799 protein, whose light-sensing function was proven to be dependent on a conserved cysteine residue at position 56, did not affect σB-mediated survival in the presence of higher intensity blue light. Phenotypic test results suggested that there may be redundancy in stress sensing between several of the RsbR paralogues but the RsbR protein plays a core structural role in stressosome formation. Novel phenotypes initially observed for the Δlmo1842 and Δlmo1642 strains were found to be caused by the presence of an RsbV I23T amino acid replacement which prevented σB activation at 37 °C but not 30 °C. Additionally, we identified that at low levels of stress, the ΔsigB mutant displayed a growth advantage over the wild-type, highlighting the energy cost associated with activating the GSR. These findings provide new insight into the mechanisms by which L. monocytogenes senses and responds to its environment and may have potential implications for control of this pathogen in food environments.en_IE
dc.subjectMicrobiologyen_IE
dc.subjectFood-borne pathogenen_IE
dc.subjectListeria Monocytogenesen_IE
dc.subjectRsbRen_IE
dc.subjectParaloguesen_IE
dc.subjectStress sensingen_IE
dc.subjectMolecular genetic investigationen_IE
dc.titleA molecular genetic investigation into stress sensing in the food-borne pathogen Listeria Monocytogenes: roles for RsbR and its paraloguesen_IE
dc.typeThesisen_IE
dc.contributor.funderScience Foundation Irelanden_IE
dc.local.noteThe food-borne pathogen Listeria monocytogenes persists in harsh environments and poses a serious concern for food industries. Here, the roles of putative stress sensor proteins were investigated with a particular focus on the response to blue light stress in order to gain greater understanding of L. monocytogenes stress survival mechanisms.en_IE
dc.description.embargo2018-02-03
dc.local.finalYesen_IE
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