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Phosphate regulation of gene expression in Vibrio parahaemolyticus
Abstract:
The synthesis of a major outer membrane protein, OmpP, in Vibrio parahaemolyticus was induced by growth in media deficient in phosphate. The gene, ompP, encoding this protein was cloned. Synthesis of OmpP in Escherichia coli was regulated by the availability of phosphate, and this control required the function of pho regulatory genes of E. coli. Analysis of gene fusion strains constructed by mutagenesis with transposon mini-Mulux revealed that ompP was transcriptionally regulated in V. parahaemolyticus. Impaired growth of a strain with an ompP defect was observed in media which contained large linear polyphosphates as the phosphate source. This and other evidence suggested that OmpP functions as a porin channel for the entry of phosphate into the cell. A number of other proteins or activities were induced by phosphate limitation including hemolysin, phospholipase C, and phosphatase activities. A regulatory locus controlling expression of phosphate-regulated genes was identified and cloned. This regulatory locus cloned from V. parahaemolyticus was shown to complement E. coli strains with defects in pho regulatory genes.
Insights
Phosphate limitation induces the outer membrane protein OmpP in Vibrio parahaemolyticus, suggesting it functions as a porin for phosphate uptake. This regulation involves specific pho genes, highlighting OmpP
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Phosphate is essential for bacterial growth and cellular processes.
- Bacterial outer membrane proteins play crucial roles in nutrient transport and environmental adaptation.
- Vibrio parahaemolyticus is a marine bacterium known to cause foodborne illness.
Purpose of the Study:
- To investigate the regulation and function of the outer membrane protein OmpP in Vibrio parahaemolyticus.
- To identify genes and regulatory mechanisms involved in phosphate acquisition in V. parahaemolyticus.
Main Methods:
- Gene cloning and characterization of the ompP gene.
- Construction and analysis of gene fusion strains using transposon mutagenesis.
- Complementation studies using E. coli pho regulatory mutants.
Main Results:
- OmpP synthesis is induced by phosphate-deficient conditions in V. parahaemolyticus.
- The ompP gene is transcriptionally regulated by phosphate availability, requiring E. coli pho regulatory genes for control in E. coli.
- A V. parahaemolyticus strain with an ompP defect exhibited impaired growth with polyphosphates, suggesting OmpP acts as a phosphate porin.
- Phosphate limitation also induced hemolysin, phospholipase C, and phosphatase activities.
- A novel regulatory locus controlling phosphate-regulated genes was identified and cloned, complementing E. coli pho mutants.
Conclusions:
- OmpP functions as a porin facilitating phosphate uptake in V. parahaemolyticus.
- Phosphate homeostasis in V. parahaemolyticus is regulated by a system involving OmpP and a novel regulatory locus.
- The identified regulatory locus shares functional homology with E. coli pho regulatory systems.