The Chemical Structure Properties and Promoting Biofilm Activity of Exopolysaccharide Produced by Shigella flexneri

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.

Polysaccharides’ Structures and Functions in Biofilm Architecture of Antimicrobial-Resistant (AMR) Pathogens

“…To evaluate the polysaccharide composition, the glycosidic bonds must be previously hydrolyzed by enzymes or acid treatment. Thereafter, monosaccharide composition and quantity can be determined by high-performance liquid chromatography (HPLC) [ 124 ] or high-performance ion exchange chromatography with pulse amperometric detection (HPAEC-PAD) [ 133 ]. In order to have information not only on the composition but also on glycosyl linkages, a sample permethylated by the Ciukanu and Kerek method [ 134 ], hydrolyzed with trifluoroacetic acid, reduced with NaBH 4 and acetylated can be analyzed by gas chromatography coupled with mass spectrometry (GC-MS) [ 133 , 135 ].…”

“…NMR is a non-invasive analysis method frequently used to finely determine a polysaccharide’s chemical structure based on the radiofrequency radiation by nuclei in a magnetic field. 1D and 2D liquid NMR analyses have been used for the characterization of purified exopolysaccharides in biofilm [ 133 , 136 ]. However, this technique has low sensitivity and requires time-consuming purification of the analytes.…”