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Physical linkage of the Vibrio cholerae mannose-sensitive hemagglutinin secretory and structural subunit gene loci:
1Department of Microbiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Abstract:
Vibrio cholerae O1 expresses a variety of cell surface factors which mediate bacterial adherence and colonization at the intestinal epithelium. The mannose-sensitive hemagglutinin (MSHA), a type IV pilus, is a potential attachment factor of the V. cholerae El Tor biotype. We describe a TnphoA mutant that is defective in its ability to hemagglutinate mouse erythrocytes. The TnphoA insertion maps to a recently identified genetic locus that encodes products that are predicted to be essential for assembly and export of the MSHA pilus. Insertional disruption at this locus in a mshA-phoA reporter strain provides evidence for a role of this locus in the latter stages of pilus assembly and/or export. These constructs have provided physical markers by which we have established close physical linkage of this secretion locus to a set of genes that includes the mshA structural gene. Sequence analysis of the intervening region between these two loci has revealed the presence of an open reading frame with homology to pilus biogenesis genes of several gram-negative bacteria. This genetic organization suggests an entire operon encoding the MSHA pilus and the components necessary for its assembly and secretion to the bacterial cell surface. The nomenclature of the MSHA structural and secretory locus has been redefined accordingly.
Insights
Researchers identified a new genetic locus essential for the assembly and export of the mannose-sensitive hemagglutinin (MSHA) pilus in Vibrio cholerae O1. This finding clarifies MSHA pilus biogenesis and secretion pathways.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Vibrio cholerae O1 utilizes cell surface factors for intestinal adherence and colonization.
- The mannose-sensitive hemagglutinin (MSHA), a type IV pilus, is a key attachment factor in the V. cholerae El Tor biotype.
Purpose of the Study:
- To investigate the genetic basis of MSHA pilus assembly and export.
- To identify and characterize the genetic locus responsible for MSHA pilus biogenesis.
Main Methods:
- Generation and analysis of TnphoA mutants in Vibrio cholerae O1.
- Hemagglutination assays using mouse erythrocytes.
- Genetic mapping and sequence analysis of the MSHA locus.
- Construction of mshA-phoA reporter strains.
Main Results:
- A TnphoA mutant exhibited a defect in hemagglutination, indicating impaired MSHA pilus function.
- The TnphoA insertion mapped to a novel genetic locus crucial for MSHA pilus assembly and export.
- Evidence suggests this locus is involved in the later stages of pilus assembly and/or export.
- Physical linkage and sequence analysis revealed an operon structure for MSHA pilus biogenesis.
Conclusions:
- A previously unidentified genetic locus is essential for MSHA pilus assembly and secretion in Vibrio cholerae O1.
- The findings elucidate the genetic organization and components involved in MSHA pilus biogenesis.
- The nomenclature for the MSHA structural and secretory locus has been updated to reflect these discoveries.