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  • Regulatory Elements Controlling Lipase and Metalloprotein Production in Pseudomonas fluorescens B52

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    Author(s)
    McCarthy, Conor
    Primary Supervisor
    Beacham, Ifor
    Other Supervisors
    Korolik, Victoria
    Year published
    2003
    Metadata
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    Abstract
    Psychrotrophic 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 ...
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    Psychrotrophic 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.
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    Thesis Type
    Thesis (PhD Doctorate)
    Degree Program
    Doctor of Philosophy (PhD)
    School
    School of Health Sciences
    DOI
    https://doi.org/10.25904/1912/1171
    Copyright Statement
    The author owns the copyright in this thesis, unless stated otherwise.
    Item Access Status
    Public
    Subject
    Pseudomonas fluorescens
    bacteria
    psychrotrophic bacteria
    psychrotrophy
    lipase
    protease
    milk spoilage
    Publication URI
    http://hdl.handle.net/10072/367432
    Collection
    • Theses - Higher Degree by Research

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