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dc.contributor.advisorBeacham, Ifor
dc.contributor.authorMcCarthy, Conor Neil
dc.date.accessioned2018-01-23T02:53:33Z
dc.date.available2018-01-23T02:53:33Z
dc.date.issued2003
dc.identifier.doi10.25904/1912/1171
dc.identifier.urihttp://hdl.handle.net/10072/367432
dc.description.abstractPsychrotrophic bacteria, such as Pseudomonas fluorescens B52, are a major cause of milk spoilage at refrigeration temperature due to the production of lipolytic and proteolytic enzymes. Regulatory mechanisms controlling the production of lipase and protease by the B52 lipA and aprX genes were investigated. Transposon mutagenesis identified the possible involvement of a poly-A polymerase enzyme which destabilises mRNA by 3' polyadenylation. A homologue of the E. coli EnvZ/OmpR two-component sensor/regulator system was identified by transposon mutagenesis and shown to repress lipase and protease production. This system responds to Na+ and K+ concentration in E. coli and these ions were also shown to repress lipase and protease expression in B52, however the EnvZ/OmpR system is not solely responsible for this. Assays of translational lacZ fusions with aprX and lipA were used to speculate on the mechanism by which Na+ and EnvZ/OmpR repress the aprX-lipA operon. A membrane-bound sensor, MspA, which regulates protease production in P. fluorescens LS107d2, was shown to exist in B52 but mutagenesis of the B52 mspA gene had no effect on lipase and protease expression. A homologue of the P. fluorescens CHA0 rsmA gene, encoding an RNA-binding translation repressor, was found in B52. Although aprX and possibly lipA contain consensus sequences for RsmA, mutagenesis of rsmA had no significant effect on lipase and protease expression. Repression of lipase and protease expression by Na+ was increased by expression of the P. fluorescens M114 pbrA sigma-factor gene in B52.
dc.languageEnglish
dc.publisherGriffith University
dc.publisher.placeBrisbane
dc.rights.copyrightThe author owns the copyright in this thesis, unless stated otherwise.
dc.subject.keywordsPseudomonas fluorescens
dc.subject.keywordsbacteria
dc.subject.keywordspsychrotrophic bacteria
dc.subject.keywordspsychrotrophy
dc.subject.keywordslipase
dc.subject.keywordsprotease
dc.subject.keywordsmilk spoilage
dc.titleRegulatory Elements Controlling Lipase and Metalloprotein Production in Pseudomonas fluorescens B52
dc.typeGriffith thesis
gro.rights.copyrightThe author owns the copyright in this thesis, unless stated otherwise.
gro.hasfulltextFull Text
dc.contributor.otheradvisorKorolik, Victoria
dc.rights.accessRightsPublic
gro.identifier.gurtIDgu1315972589781
gro.identifier.ADTnumberadt-QGU20031015.124744
gro.source.ADTshelfnoADT0
gro.source.GURTshelfnoGURT
gro.thesis.degreelevelThesis (PhD Doctorate)
gro.thesis.degreeprogramDoctor of Philosophy (PhD)
gro.departmentSchool of Health Sciences
gro.griffith.authorMcCarthy, Conor


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