Abstract
Shigella flexneri is a waterborne and foodborne pathogen that can damage human health. The exopolysaccharides (S-EPS) produced by S. flexneri CMCC51574 were found to promote biofilm formation and virulence. In this research, the crude S-EPS produced by S. flexneri CMCC51574 were separated into three main different fractions, S-EPS 1-1, S-EPS 2-1, and S-EPS 3-1. The structure of the S-ESP 2-1 was identified by FT-IR, ion chromatography analysis, methylation analysis, and NMR analysis. The main chain of S-EPS 2-1 was α-Manp-(1 → 3)-α-Manp-[(1 → 2,6)-α-Manp]15-[(1 → 2)-Manf-(1→]8; there were two branched-chain R1 and R2 with a ratio of 4:1, R1: α-Manp-(1 → 6)- and R2: α-Manp-(1 → 6)- Glc-(1 → 6)- were linked with (1 → 2,6)-α-Manp. It was found that S-EPS 2-1 exhibited the highest promoting effect on biofilm formation of S. flexneri. The S-EPS 2-1 was identified to interact with extracellular DNA (eDNA) of S. flexneri, indicating that the S-EPS 2-1 was the specific polysaccharide in the spatial structure of biofilm formation. Our research found the important role of S-EPS in S. flexneri biofilm formation, which will help us to understand the underlining mechanisms of the biofilm formation and find effective ways to prevent S. flexneri biofilm infection.
Highlights
Bacteria exhibit two modes of growth: the free-living planktonic mode or the sessile, surfaceattached mode within biofilms, which are structured communities encased in a self-produced polymer matrix mainly including exopolysaccharide, protein, and extracellular DNA (Rabin et al, 2015; Kim and Lee, 2016; Zhao et al, 2017; Rumbaugh and Sauer, 2020)
We focused on the important role of specific polysaccharides and DNA in the spatial structure of biofilm formation of S. flexneri
The results showed that the S-EPS produced by S. flexneri were mixtures of fractions S-EPS 1-1, S-EPS 2-1, and S-EPS 3-1
Summary
Bacteria exhibit two modes of growth: the free-living planktonic mode or the sessile, surfaceattached mode within biofilms, which are structured communities encased in a self-produced polymer matrix mainly including exopolysaccharide, protein, and extracellular DNA (eDNA) (Rabin et al, 2015; Kim and Lee, 2016; Zhao et al, 2017; Rumbaugh and Sauer, 2020). Once pathogens form the biofilm, it will cause long-term continuous infection and be difficult to exterminate, which is common in daily living, food processing, and medical environments. The pathogen can further enhance its tolerance to antibiotics by forming biofilm (Jiang et al, 2011; Hall and Mah, 2017; Roy et al, 2018). It is extremely important to explore the methods to exterminate the pathogen’s biofilm, and to explore the potential mechanism of pathogen biofilm formation
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