Structural basis of host recognition and biofilm formation by Salmonella Saf pili

• Published in: eLife Vol. 6
• Main Authors: Zeng, Longhui, Zhang, Li, Wang, Pengran, Meng, Guoyu
• Format: Journal Article
• Language: English
• Published: England eLife Sciences Publications Ltd 10.11.2017; eLife Sciences Publications, Ltd
• Subjects: Adhesives; Bacteria; Bacterial Adhesion; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; biofilm formation; Biofilms; Biofilms - growth & development; Cell aggregation; Colonization; Crystallography; Crystallography, X-Ray; Fimbriae, Bacterial - physiology; host recognition; Hydrogen bonding; Life sciences; Microbiology and Infectious Disease; Models, Molecular; Oligomerization; Pili; poly-adhesive activity; Protein Binding; Protein Conformation; Protein Multimerization; Salmonella; Salmonella atypical fimbriae; Salmonella Typhimurium; Salmonella typhimurium - physiology; self-associating oligomerization; Self-association; Structure-function relationships; poly-adhesive activity; self-associating oligomerization; Salmonella atypical fimbriae; infectious disease; host recognition; microbiology; S. enterica serovar typhi; biofilm formation
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.28619

Pili are critical in host recognition, colonization and biofilm formation during bacterial infection. Here, we report the crystal structures of SafD-dsc and SafD-SafA-SafA (SafDAA-dsc) in Saf pili. Cell adherence assays show that SafD and SafA are both required for host recognition, suggesting a poly-adhesive mechanism for Saf pili. Moreover, the SafDAA-dsc structure, as well as SAXS characterization, reveals an unexpected inter-molecular oligomerization, prompting the investigation of Saf-driven self-association in biofilm formation. The bead/cell aggregation and biofilm formation assays are used to demonstrate the novel function of Saf pili. Structure-based mutants targeting the inter-molecular hydrogen bonds and complementary architecture/surfaces in SafDAA-dsc dimers significantly impaired the Saf self-association activity and biofilm formation. In summary, our results identify two novel functions of Saf pili: the poly-adhesive and self-associating activities. More importantly, Saf-Saf structures and functional characterizations help to define a pili-mediated inter-cellular oligomerizaiton mechanism for bacterial aggregation, colonization and ultimate biofilm formation.