Regulation of Exopolysaccharide Production in Myxococcus Xanthus

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dc.contributor.authorBlack, Wesley P.en
dc.contributor.committeechairYang, Zhaominen
dc.contributor.committeememberSible, Jill C.en
dc.contributor.committeememberPopham, David L.en
dc.contributor.committeememberStevens, Ann M.en
dc.contributor.departmentBiologyen
dc.date.accessioned2014-03-14T20:21:08Zen
dc.date.adate2006-01-06en
dc.date.available2014-03-14T20:21:08Zen
dc.date.issued2005-12-15en
dc.date.rdate2009-01-06en
dc.date.sdate2005-12-23en
dc.description.abstractThe surface gliding motility of Myxococcus xanthus is required for a multicellular developmental process initiated by unfavorable growth conditions. One form of the M. xanthus surface motility, social (S) gliding, is mediated by the extension and retraction of polarly localized type IV pili (Tfp). Besides Tfp, exopolysaccharides (EPS), another cell surface associated component, are also required for M. xanthus S motility. Previous studies demonstrated that the Dif chemotaxis-like signal transduction pathway is central to the regulation of EPS production in M. xanthus. Specifically, difA, difC and difE mutants were found to be defective in EPS production and S motility. DifA, DifC and DifE, homologous to methyl-accepting chemotaxis proteins (MCPs), CheW and CheA, respectively, are therefore positive regulators of EPS. This study, undertaken to better understand the regulation of EPS production, led to a few major findings. First, DifD and DifG, homologous to CheY and CheC, respectively, were found to be negative regulators of EPS production. Both DifD and DifG likely function upstream of the DifE kinase in EPS regulation. DifB, which has no homology to known chemotaxis proteins, was found not to be involved in EPS production. Secondly, this study led to the recognition that Tfp likely function upstream of the Dif pathway in the regulation of EPS production. Extracellular complementation experiments suggest that Tfp may act as sensors instead of signals for the Dif chemotaxis-like pathway. We propose a regulatory feedback loop that couples EPS production with Tfp function through the Dif signaling proteins. Lastly, we sought to identify additional genes involved in EPS production. Our efforts identified a mutation in a separate chemotaxis gene cluster as a suppressor of difA mutations, suggesting potential cross-talks among the multiple chemotaxis-like pathways in M. xanthus. In addition, we identified twenty-five previously uncharacterized genes that are predicted to be involved in M. xanthus EPS production. These genes appear to encode additional EPS regulators and proteins with biosynthetic function.en
dc.description.degreePh. D.en
dc.identifier.otheretd-12232005-042454en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-12232005-042454/en
dc.identifier.urihttp://hdl.handle.net/10919/30250en
dc.publisherVirginia Techen
dc.relation.haspartWesBlack_Dissertation.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectDif chemotaxis proteinsen
dc.subjectgliding motilityen
dc.subjectfruiting body developmenten
dc.subjectMyxococcus xanthusen
dc.subjectexopolysaccharide (EPS)en
dc.subjectsignal transductionen
dc.subjecttype IV pili (Tfp)en
dc.titleRegulation of Exopolysaccharide Production in Myxococcus Xanthusen
dc.typeDissertationen
thesis.degree.disciplineBiologyen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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