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

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Abstract

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.

Data availability

The following data sets were generated

1. Zeng LH
2. Zhang L
3. Wang PR
4. Meng G
(2017) Crystal structure of Salmonella SafD adhesin
5Y9G.

http://www.pdb.org
1. Zeng LH
2. Zhang L
3. Wang PR
4. Meng G
(2017) Crystal structure of SafDAA-dsc complex
5Y9H.

http://www.pdb.org

Article and author information

Author details

Longhui Zeng

State Key Laboratory of Medical Genomics, Shanghai JiaoTong University, Shanghai, China

Competing interests
The authors declare that no competing interests exist.
Li Zhang

State Key Laboratory of Medical Genomics, Shanghai JiaoTong University, Shanghai, China

Competing interests
The authors declare that no competing interests exist.
Pengran Wang

State Key Laboratory of Medical Genomics, Shanghai JiaoTong University, Shanghai, China

Competing interests
The authors declare that no competing interests exist.
Guoyu Meng

State Key Laboratory of Medical Genomics, Shanghai JiaoTong University, Shanghai, China

For correspondence
guoyumeng@shsmu.edu.cn

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0001-7904-2382

Funding

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.