Localization and Dynamics of the Cell Shape-Determining Csd2 Protein Complex in H. pylori.

Approximately half of the world population is infected with the human pathogen Helicobacter pylori, which causes gastric inflammation, chronic gastritis, or peptide ulceration. A significant factor in the colonization of the upper digestive system is the helical shape of H. pylori. This helical form is maintained by a complex network of peptidoglycan (PG)-modifying enzymes and cytoskeletal proteins. Among these, the D,D-endopeptidase Csd2 plays a central role, working in conjunction with other cell shape-determining (Csd) proteins. Csd1 and Csd2 have been categorized as members of the M23B metallopeptidase family. These enzymes are classified as D,D-endopeptidases, and their function involves the cleavage of the D-Ala4-mDAP3 bond, which is present in the cross-linked di-mer muropeptides. Despite the fact that the structure of the Csd1:Csd2 complex has been examined via biochemical methods, information on the in vivo localization and dynamics of D,D-endopeptidases is still missing. Here, we use an approach that employs sophisticated different microscopy methods to visualize the spatial temporal localization and dynamics of Csd2, involving both structured illumination microscopy and single-molecule tracking. Our findings thus contribute to refining the existing model for this cellular complex by revealing curvature-dependent spatial organization and temporal dynamics underlying peptidoglycan remodeling processes essential for helical cell shape formation and maintenance. Understanding the dynamics provides insight into the mechanisms that maintain bacterial morphology and potential targets for therapeutic intervention.