Antibacterial Activity of Sulfated Galactans from Eucheuma serra and Gracilari verrucosa against Diarrheagenic Escherichia coli via the Disruption of the Cell Membrane Structure.

Yixiang Liu,Yanbo Wang,Donghui Li,Min-Jie Cao,Guang-Ming Liu,Chao Zou,Wenqiang Liu,Ling Huang,Yu Ma,Zhaohua Chen

doi:10.3390/md18080397

Abstract

Seaweed sulfated polysaccharides have attracted significant attention due to their antibacterial activity. This work investigated the antibacterial activity and mechanism of depolymerized sulfated galactans from Eucheuma serra (E. serra) and Gracilaria verrucosa (G. verrucosa) against enterotoxigenic Escherichia coli (ETEC) K88. The results show that removing the metal ions improves the anti-ETEC K88 activity of the galactans. The fluorescence labeling study confirmed that the sulfated galactans penetrated the cell walls and eventually reached the interior of the ETEC K88. Nucleic acid staining and intracellular protein leakage were also observed, indicating the destruction of permeability and integrity of the cell membrane. Interestingly, the two polysaccharides exhibited no effect on the proliferation of the selected Gram-positive bacteria and yeast. This indicates that the cell wall structure of the microorganisms could influence the bacteriostatic activity of the sulfated polysaccharides, as well. These results suggest that the sulfated seaweed polysaccharides might have potential application value in antibacterial diarrhea.

Highlights

Enterotoxigenic Escherichia coli (ETEC) is a kind of Gram-negative bacterium that can express a variety of membrane mucins, adhere to intestinal epithelial cells, and secrete enterotoxin to cause vomiting and diarrhea [1]
This study investigated how the anti-enterotoxigenic Escherichia coli (ETEC) K88 activity of sulfated galactans is enhanced by metal ion desorption since algae are responsible for enriching seawater with metal ions
Indicates that the ash content in E. serra sulfated polysaccharide (ESP) and G. verrucosa sulfated polysaccharide (GSP) remained high at 17.8% and 13.2%, respectively, after ultrafiltration in the absence of a metal ion chelating agent in the eluent

Summary

Introduction

Enterotoxigenic Escherichia coli (ETEC) is a kind of Gram-negative bacterium that can express a variety of membrane mucins, adhere to intestinal epithelial cells, and secrete enterotoxin to cause vomiting and diarrhea [1]. This pathogen is responsible for almost 600,000 deaths every year in most underdeveloped countries and regions, and mainly include children under 5 years old [2]. Antibiotics remain the primary treatment for ETEC-induced diarrhea, and this type of treatment is extremely effective and inexpensive, the long-term use of antibiotics causes bacterial resistance.

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