Peptidoglycan Crosslinking Relaxation Promotes Helicobacter pylori's Helical Shape and Stomach Colonization

Abstract

Summary The mechanisms by which bacterial cells generate helical cell shape and its functional role are poorly understood. Helical shape of the human pathogen Helicobacter pylori may facilitate penetration of the thick gastric mucus where it replicates. We identified four genes required for helical shape: three novel LytM peptidoglycan endopeptidase homologues (csd1–3) and a ccmA homologue. Surrounding the cytoplasmic membrane of most bacteria, the peptidoglycan (murein) sacculus is a meshwork of glycan strands joined by peptide cross-links. Intact cells and isolated sacculi from mutants lacking any single csd gene or ccmA formed curved rods and showed increased peptidoglycan cross-linking. Quantitative morphological analyses of multiple-gene deletion mutants revealed each protein uniquely contributes to a shape-generating pathway. This pathway is required for robust colonization of the stomach in spite of normal directional motility. Our findings suggest that the coordinated action of multiple proteins relaxes peptidoglycan cross-linking, enabling helical cell curvature and twist.

β-Helical architecture of cytoskeletal bactofilin filaments revealed by solid-state NMR

“…S1). The two samples yielded essentially identical results, with a very high spectral resolution for carbons of around 0.25-0.6 ppm (full-width at half-height, FWHH) and for nitrogens of 0.5-0.8 ppm (see 13 C trace in Fig. 1C and 13 C and 15 N traces in SI Appendix, Fig.…”

“…This fact allowed us to use the obtained 13 C and 15 N chemical shifts to determine the secondary structure of the BacA filament core. First, structural predictions were derived from secondary chemical shift values (Δδ CA -Δδ CB ) (Fig.…”

“…The pellets were then transferred into magic-angle spinning (MAS) rotors and subjected to ssNMR analysis. All spectra were recorded on either a Bruker Avance II 850 MHz wide-bore or an 800 MHz narrow-bore spectrometer equipped with 3.2 and 4 mm triple-resonance ( 1 H, 13 C, 15 N) MAS probe heads. The sample temperature was kept at around 4°C, as measured by the temperature-dependent position of the water resonance peak with respect to internal DSS.…”

“…BacP, on the other hand, assembles into short filamentous structures that emanate from the cell poles, recruiting and thus controlling a small GTPase involved in type IV pili-dependent motility (12). As another well-characterized example, the e-proteobacterium Helicobacter pylori, a human pathogen notorious for causing peptic ulcers, was shown to depend on a bactofilin homolog (CcmA) for maintaining its characteristic helical cell shape, a feature required for cells to efficiently colonize the gastric mucus (13). Moreover, in the γ-proteobacterium Proteus mirabilis, a homolog of the bactofilin CcmA has been implicated in cell shape and swarming motility (14).…”

Getting into shape: How do rod-like bacteria control their geometry?

“…There are additional, fascinating questions associated with the intersection of mechanics and bacterial growth, that we shall not discuss here, such as the forces exerted by the Z-ring in the bacterial division process (Egan and Vollmer 2013;Li et al 2013;Piro et al 2013;Sun and Jiang 2011), the role of crescentin in shaping curved cells (Cabeen et al 2009), and the growth of curved and helical bacteria (Sycuro et al 2010;Typas et al 2011), to name but a few.…”