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Perfringolysin O expression in Clostridium perfringens is independent of the upstream pfoR gene
1Bacterial Pathogenesis Research Group, Department of Microbiology, Monash University, Victoria 3800, Australia.
Abstract:
The pathogenesis of Clostridium perfringens-mediated gas gangrene or clostridial myonecrosis involves the extracellular toxins alpha-toxin and perfringolysin O. Previous studies (T. Shimizu, A. Okabe, J. Minami, and H. Hayashi, Infect. Immun. 59:137-142, 1991) carried out with Escherichia coli suggested that the perfringolysin O structural gene, pfoA, was positively regulated by the product of the upstream pfoR gene. In an attempt to confirm this hypothesis in C. perfringens, a pfoR-pfoA deletion mutant was complemented with isogenic pfoA(+) shuttle plasmids that varied only in their ability to encode an intact pfoR gene. No difference in the ability to produce perfringolysin O was observed for C. perfringens strains carrying these plasmids. In addition, chromosomal pfoR mutants were constructed by homologous recombination in C. perfringens. Again no difference in perfringolysin O activity was observed. Since it was not possible to alter perfringolysin O expression by mutation of pfoR, it was concluded that the pfoR gene product is unlikely to have a role in the regulation of pfoA expression in C. perfringens.
Insights
The pfoR gene does not regulate perfringolysin O production in Clostridium perfringens. Studies found no change in perfringolysin O activity when pfoR was mutated or complemented, suggesting pfoR is not involved in pfoA regulation.
Area of Science:
- Microbiology
- Molecular Biology
- Pathogenesis
Background:
- Clostridium perfringens causes gas gangrene via toxins like perfringolysin O.
- Previous research suggested the pfoR gene regulates the perfringolysin O gene (pfoA) in E. coli.
Purpose of the Study:
- To investigate the role of the pfoR gene in regulating perfringolysin O (pfoA) expression in Clostridium perfringens.
- To confirm or refute the hypothesis that pfoR positively regulates pfoA.
Main Methods:
- Constructed a pfoR-pfoA deletion mutant in C. perfringens.
- Complemented the mutant with shuttle plasmids encoding pfoA, with and without pfoR.
- Created chromosomal pfoR mutants using homologous recombination.
Main Results:
- Complementing the deletion mutant with plasmids did not alter perfringolysin O production.
- Chromosomal pfoR mutants showed no difference in perfringolysin O activity compared to wild-type.
- Perfringolysin O expression remained unchanged despite pfoR mutations.
Conclusions:
- The pfoR gene product is unlikely to play a role in the regulation of pfoA expression in Clostridium perfringens.
- The hypothesis of positive regulation of pfoA by pfoR in C. perfringens was not supported by experimental evidence.