Gastrointestinal signals in supplemented media reveal a role in adherence for the Shigella flexneri sap autotransporter gene

ABSTRACT

Shigella flexneri causes severe diarrheal disease worldwide. While many aspects of pathogenesis have been elucidated, significant knowledge gaps remain regarding the role of putative chromosomally-encoded virulence genes. The uncharacterized sap gene encoded on the chromosome has significant nucleotide sequence identity to the fluffy (flu) antigen 43 autotransporter gene in pathogenic Escherichia coli. Here, we constructed a Δsap mutant in S. flexneri strain 2457T and examined the effects of this mutation on bacterial cell aggregation, biofilm formation, and adherence to colonic epithelial cells. Analyses included the use of growth media supplemented with glucose and bile salts to replicate small intestinal signals encountered by S. flexneri. Deletion of the sap gene in 2457T affected epithelial cell adherence, resulted in quicker bacterial cell aggregation, but did not affect biofilm formation. This work highlights a functional role for the sap gene in S. flexneri pathogenesis and further demonstrates the importance of using relevant and appropriate gastrointestinal signals to characterize virulence genes of enteropathogenic bacteria.

KEYWORDS:

• Shigella flexneri
• adherence factors
• bile salts
• glucose
• autotransporter
• sap

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that data supporting the findings of this study are available within the article or upon request from the corresponding author.

Additional information

Funding

This work was supported in part by the National Institute of Allergy and Infectious Diseases (NIAID) grant K22AI104755 and MGH ECOR grants 2020A003037 and 2022A009041 awarded to CSF. Additional salary support was provided by the NIAID grant R21AI146405 for YL and CSF, Ecole Normale Superieur Paris-Saclay for RH, and NIAID grant U19AI110820 for DAR. The funders had no role in the study design, data collection and analysis, decision to publish, or manuscript preparation. The content is the sole responsibility of the authors and does not necessarily represent the official views of the funders