Helicobacter pylori flagellar hook-filament transition is controlled by a FliK functional homolog encoded by the gene
Kieran A Ryan1, Najma Karim, Mulugeta Worku
1Department of Microbiology and Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland.
Abstract:
Helicobacter pylori is a human gastric pathogen which is dependent on motility for infection. The H. pylori genome encodes a near-complete complement of flagellar proteins compared to model enteric bacteria. One of the few flagellar genes not annotated in H. pylori is that encoding FliK, a hook length control protein whose absence leads to a polyhook phenotype in Salmonella enterica. We investigated the role of the H. pylori gene HP0906 in flagellar biogenesis because of linkage to other flagellar genes, because of its transcriptional regulation pattern, and because of the properties of an ortholog in Campylobacter jejuni (N. Kamal and C. W. Penn, unpublished data). A nonpolar mutation of HP0906 in strain CCUG 17874 was generated by insertion of a chloramphenicol resistance marker. Cells of the mutant were almost completely nonmotile but produced sheathed, undulating polyhook structures at the cell pole. Expression of HP0906 in a Salmonella fliK mutant restored motility, confirming that HP0906 is the H. pylori fliK gene. Mutation of HP0906 caused a dramatic reduction in H. pylori flagellin protein production and a significant increase in production of the hook protein FlgE. The HP0906 mutant showed increased transcription of the flgE and flaB genes relative to the wild type, down-regulation of flaA transcription, and no significant change in transcription of the flagellar intermediate class genes flgM, fliD, and flhA. We conclude that the H. pylori HP0906 gene product is the hook length control protein FliK and that its function is required for turning off the sigma(54) regulon during progression of the flagellar gene expression cascade.
Insights
The Helicobacter pylori HP0906 gene, identified as fliK (flagellar hook length protein), is crucial for bacterial motility. Its absence results in polyhook structures and impaired flagellar gene regulation, impacting infection.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Helicobacter pylori is a gastric pathogen reliant on motility for infection.
- The H. pylori genome lacks a known gene for FliK, a protein controlling flagellar hook length in other bacteria.
- The HP0906 gene was investigated due to its location, transcriptional patterns, and similarity to Campylobacter jejuni orthologs.
Purpose of the Study:
- To investigate the function of the H. pylori gene HP0906 in flagellar biogenesis.
- To determine if HP0906 encodes the flagellar hook length control protein FliK.
- To elucidate the role of HP0906 in regulating flagellar gene expression.
Main Methods:
- A nonpolar mutation was created in the HP0906 gene using a chloramphenicol resistance marker.
- The motility and flagellar structure of the mutant strain were analyzed.
- HP0906 was expressed in a Salmonella fliK mutant to assess functional complementation.
- Gene and protein expression levels (flagellin, FlgE) and transcript levels (flgE, flaB, flaA, flgM, fliD, flhA) were quantified.
Main Results:
- HP0906 mutants exhibited near-complete non-motility and formed polyhook structures.
- Complementation of a Salmonella fliK mutant with HP0906 restored motility, confirming it as H. pylori fliK.
- Mutation of HP0906 led to reduced flagellin production, increased FlgE production, and altered transcription of flagellar genes, including down-regulation of flaA.
- The mutant showed increased transcription of flgE and flaB but no significant change in intermediate flagellar genes.
Conclusions:
- The H. pylori HP0906 gene product is confirmed as the flagellar hook length control protein FliK.
- H. pylori FliK is essential for proper flagellar assembly, controlling hook length and polyhook formation.
- FliK is required for the timely downregulation of the sigma(54) regulon during flagellar gene cascade progression, impacting overall flagellar gene expression.
Related Concept Videos
01:18Flagella and Motility in Bacteria
01:28Fimbriae, Pili, and Axial Filaments
01:29Cytoskeletal Proteins in Bacteria
00:55DNA Helicases
01:26Gastritis II: Pathophysiology
01:39Mechanism of Filopodia Formation
Their main function is to guide migrating cells during normal tissue morphogenesis or cancer metastasis by recognizing and making initial contacts with the extracellular matrix. However, they can also act as stationary cell anchors or help to establish communication...