Genetic regulation of virulence in Francisella tularensis

dc.contributor.advisorKlose, Karl E.
dc.contributor.authorRodriguez, Stephen A.
dc.contributor.committeeMemberSeshu, Janakiram
dc.contributor.committeeMemberArulanandam, Bernard P.
dc.contributor.committeeMemberGuentzel, Neal
dc.contributor.committeeMemberDube, Peter H.
dc.date.accessioned2024-02-12T19:51:18Z
dc.date.available2024-02-12T19:51:18Z
dc.date.issued2010
dc.descriptionThis item is available only to currently enrolled UTSA students, faculty or staff. To download, navigate to Log In in the top right-hand corner of this screen, then select Log in with my UTSA ID.
dc.description.abstract<italic>Francisella tularensis</italic> is the causal agent of the zoonotic disease tularemia, and a potential biological weapon. Because studying the molecular mechanisms of pathogenesis has been difficult due to a lack of techniques for targeted gene disruption, we have adapted a gene knockout system that efficiently targets genes for disruption in <italic>F. tularensis</italic>. This system utilizes mobile group II introns (targetrons) specifically optimized for <italic>F. tularensis</italic>. Results showed that this system is effective across <italic>F. tularensis</italic> subspecies, and enables simultaneous inactivation of duplicate genes, which should prove useful in targeting duplicated virulence genes in the highly virulent strains. The virulence of <italic>F. tularensis</italic> is dependent on the genes encoded within the <italic>Francisella</italic> Pathogenicity Island (FPI). The FPI has recently been shown to encode a secretion system related to Type VI secretion systems found in other pathogenic bacteria. A single FPI is found in <italic>F. tularensis</italic> spp. <italic>novicida</italic>, which has low virulence for humans, whereas two identical FPIs are found in the highly virulent <italic>F. tularensis</italic> spp. <italic>tularensis</italic>. We utilized FLP recombinase-mediated excision to remove the entire FPI from <italic>F. tularensis</italic> spp. <italic>novicida</italic>. The resultant &#8710;FPI mutant was defective for intramacrophage replication, and was attenuated for virulence in mice. These results emphasize the importance of the FPI to <italic>F. tularensis</italic> spp. <italic>novicida</italic> virulence. Moreover, the FLP recombinase-mediated excision technique should prove useful in analyzing the duplication of the FPI in <italic>F. tularensis</italic> spp. <italic>tularensis</italic>. The FPI gene <italic>iglE</italic> encodes a putative lipoprotein with a predicted lipobox that may be part of the T6SS-like secretion system. We constructed an <italic>iglE</italic> mutant <italic>F. tularensis</italic> spp. <italic>novicida</italic> strain, and demonstrated that <italic>iglE</italic> contributes to intramacrophage replication. Membrane fractionation of <italic>F. tularensis</italic> expressing IglE-FLAG demonstrated that this protein is found in the outer membrane (OM), but mutation of the putative site of lipidation (C22G) prevents OM localization of IglE-FLAG. Additionally, OM localization of another FPI protein, IglA, appeared to require IglE, suggesting that IglE may facilitate localization of IglA. Further experiments will clarify the contribution of iglE to the pathogenesis of <italic>F. tularensis</italic>. The genetic techniques that have been developed and the investigation of IglE should contribute to deciphering the virulence of <italic>F. tularensis</italic>.
dc.description.departmentIntegrative Biology
dc.format.extent169 pages
dc.format.mimetypeapplication/pdf
dc.identifier.isbn9781109758221
dc.identifier.urihttps://hdl.handle.net/20.500.12588/5128
dc.languageen
dc.subjectFPI
dc.subjectFrancisella tularensis
dc.subjectlipoprotein
dc.subjectpathogenicity island
dc.subjectsecretion system
dc.subjecttargetron
dc.subject.classificationMicrobiology
dc.subject.classificationMolecular biology
dc.subject.classificationGenetics
dc.titleGenetic regulation of virulence in Francisella tularensis
dc.typeThesis
dc.type.dcmiText
dcterms.accessRightspq_closed
thesis.degree.departmentIntegrative Biology
thesis.degree.grantorUniversity of Texas at San Antonio
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy

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