FlgV forms a flagellar motor ring that is required for optimal motility of Helicobacter pylori

The impact of the flagellar protein gene fliK on Helicobacter pylori biofilm formation

The biofilm structure of Helicobacter pylori is known to enhance its capabilities for antimicrobial resistance. This study aims to investigate the role of the flagellar hook length control protein gene fliK in the biofilm formation of H. pylori. Homologous recombination was employed to knock out the fliK gene in the H. pylori NCTC 11637 strain. The flagella of H. pylori were observed using transmission electron microscopy (TEM), whereas H. pylori motility and growth were examined through semi-solid agar assays and growth curve analyses, respectively. The bacterial biofilm and its constituents were visualized utilizing fluorescence confocal microscopy. Assessments of H. pylori adhesion to gastric mucosal cells, its vacuolar toxicity, and antibiotic resistance were evaluated using co-culture experiments and E-test methods. The fliK gene was successfully knocked out in H. pylori NCTC 11637. The ΔfliK mutant exhibited polyhook structures or lacked typical flagellar morphology, reduced mobility, and a slower bacterial growth rate compared with the wild-type strain. Fluorescence confocal microscopy revealed a decrease in the thickness of the biofilm formed by the ΔfliK strain, along with reductions in polysaccharide and DNA components. The deletion of fliK did not affect vacuolar toxicity or antibiotic resistance but did reduce the adhesive capacity of the bacterium to gastric mucosal cells. The deletion of the fliK gene significantly impairs H. pylori biofilm formation, leading to substantial decreases in biofilm components, bacterial growth, and adhesion capabilities. These findings underscore the importance of fliK in the pathogenicity of H. pylori.IMPORTANCEThe increasing antibiotic resistance of Helicobacter pylori has emerged as a global health concern, with biofilm formation serving as a crucial mechanism underlying this resistance. This study investigates the role of the fliK gene, which encodes the flagellar hook length control protein, in H. pylori biofilm formation. Furthermore, we examined the influence of fliK on H. pylori growth, motility, and cellular adhesion capabilities. Our findings elucidate the molecular mechanisms governing H. pylori biofilm formation and suggest potential therapeutic strategies for addressing H. pylori antibiotic resistance.

FlgY, PflA, and PflB form a spoke-ring network in the high-torque flagellar motor of Helicobacter pylori

Helicobacter pylori has evolved distinct flagellar motility to colonize the human stomach. Rotation of the H. pylori flagella is driven by one of the largest known bacterial flagellar motors. In addition to the core motor components found in Escherichia coli and Salmonella enterica, the flagellar motor in H. pylori possesses many accessories that enable the bacteria to penetrate the gastric mucus layer. Here, we utilize cryoelectron tomography with molecular genetics and biochemical approaches to characterize three accessory proteins, FlgY, PflA, and PflB, and their roles in H. pylori flagellar assembly and motility. Comparative analyses of in situ flagellar motor structures from pflA, pflB, and flgY mutants and wild-type H. pylori reveal that FlgY forms a 13-fold proximal spoke-ring around the MS-ring and that PflA and PflB form an 18-fold distal spoke-ring enclosing 18 torque-generating stator complexes. We build a pseudoatomic model of the H. pylori motor by leveraging AlphaFold-predicted structures, protein-protein interactions, and in situ motor structures. Our model suggests that the FlgY spoke-ring functions as a bearing around the rotating MS-ring and as a template for stabilizing the PflA-PflB spoke-ring, thus enabling the recruitment of 18 stator complexes for high-torque generation. Overall, our study sheds light on how this spoke-ring network between the MS-ring and stator complexes enables the unique motility of H. pylori. As these accessory proteins are conserved in the phylum Campylobacterota, our findings apply broadly to a better understanding of how polar flagella help bacteria thrive in gastric and enteric niches.

Broadly conserved FlgV controls flagellar assembly and Borrelia burgdorferi dissemination in mice

Flagella propel pathogens through their environments, yet are expensive to synthesize and are immunogenic. Thus, complex hierarchical regulatory networks control flagellar gene expression. Spirochetes are highly motile bacteria, but peculiarly, the archetypal flagellar regulator σ28 is absent in the Lyme spirochete Borrelia burgdorferi. Here, we show that gene bb0268 (flgV) in B. burgdorferi, previously and incorrectly annotated to encode the RNA-binding protein Hfq, is instead a structural flagellar component that modulates flagellar assembly. The flgV gene is broadly conserved in the flagellar superoperon alongside σ28 in many Spirochaetae, Firmicutes and other phyla, with distant homologs in Epsilonproteobacteria. We find that B. burgdorferi FlgV is localized within flagellar basal bodies, and strains lacking flgV produce fewer and shorter flagellar filaments and are defective in cell division and motility. During the enzootic cycle, flgV-deficient B. burgdorferi survive and replicate in Ixodes ticks but are attenuated for infection and dissemination in mice. Our work defines infection timepoints when spirochete motility is most crucial and implicates FlgV as a broadly distributed structural flagellar component that modulates flagellar assembly.

Broadly conserved FlgV controls flagellar assembly and Borrelia burgdorferi dissemination in mice

Flagella propel pathogens through their environments yet are expensive to synthesize and are immunogenic. Thus, complex hierarchical regulatory networks control flagellar gene expression. Spirochetes are highly motile bacteria, but peculiarly in the Lyme spirochete Borrelia burgdorferi, the archetypal flagellar regulator σ28 is absent. We rediscovered gene bb0268 in B. burgdorferi as flgV, a broadly-conserved gene in the flagellar superoperon alongside σ28 in many Spirochaetes, Firmicutes and other phyla, with distant homologs in Epsilonproteobacteria. We found that B. burgdorferi FlgV is localized within flagellar motors. B. burgdorferi lacking flgV construct fewer and shorter flagellar filaments and are defective in cell division and motility. During the enzootic cycle, B. burgdorferi lacking flgV survive and replicate in Ixodes ticks but are attenuated for dissemination and infection in mice. Our work defines infection timepoints when spirochete motility is most crucial and implicates FlgV as a broadly distributed structural flagellar component that modulates flagellar assembly.