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An environmentally regulated pilus-like appendage involved in Campylobacter pathogenesis
1Department of Biochemistry and Microbiology, University of Victoria, British Columbia, Canada.
Molecular Microbiology
|May 1, 1996
Summary
Bile salts induce pilus production in Campylobacter bacteria, with deoxycholate and chenodeoxycholic acid being particularly effective. A specific gene, pspA, is crucial for this pilus synthesis, impacting disease severity but not colonization.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Campylobacter species are significant human pathogens.
- Pilus-like appendages in bacteria can play roles in adhesion and colonization.
- The role of bile salts in Campylobacter pilus production is not well understood.
Purpose of the Study:
- To investigate the effect of bile salts on pilus production in Campylobacter species.
- To identify the genetic basis for bile-induced pilus formation.
- To assess the role of pili in Campylobacter adherence, invasion, and disease.
Main Methods:
- Electron microscopy was used to visualize pili.
- Bile salt supplements were added to bacterial growth media.
- Genetic analysis, including site-specific insertional mutagenesis of the pspA gene, was performed.
- In vitro adherence and invasion assays using INT 407 cells were conducted.
- A ferret model was used to evaluate colonization and disease symptoms.
Main Results:
- Bile salts, especially deoxycholate and chenodeoxycholic acid, significantly enhanced pilus production and bacterial aggregation.
- Pili were morphologically characterized as 4-7 nm wide and >1 micron long.
- A gene, pspA, was identified and shown to be essential for pilus synthesis.
- A non-piliated mutant (pspA mutant) did not show reduced adherence or invasion in vitro.
- The pspA mutant exhibited reduced disease symptoms in ferrets but retained colonization ability.
Conclusions:
- Bile salts are potent inducers of pilus-like appendages in Campylobacter species.
- The pspA gene is critical for bile-induced pilus production.
- While pili are not essential for in vitro adherence or invasion, they contribute to the virulence and disease-causing potential of Campylobacter in vivo.