Inhibitory effect of a polysaccharide prepared from edible red seaweed Bangia fusco-purpurea on Escherichia coli by regulating its metabolisms

In this study, the antimicrobial activity on Escherichia coli (E. coli) of a polysaccharide (BFP) prepared from Bangia fusco-purpurea with the underlying mechanism was investigated. The results showed that BFP could against the growth of E. coli in a concentration-dependent manner. The inhibitory effect of BFP on E. coli might be through disrupting the morphology, increasing the intracellular reactive oxygen species levels, and decreasing the Ca2+- Mg2+-ATPase activity in E. coli. Furthermore, BFP significantly reduced the biofilm formation in E. coli by downregulating the critical biofilm-related genes, including flhD, flhC, fliM, csgA, and csgD, especially fliM, and weakened the bacteria's infection and pathogenic potentials. Notably, the metabolomic analysis demonstrated that BFP performed antimicrobial activity mainly by up-regulating the sphingosine and phospholipids metabolites, down-regulating the amino acid metabolites, and the two-component system in E. coli. The findings advance the understanding on the underlying mechanisms of red seaweed polysaccharide BFP against E. coli, and further provide the scientific basis for developing BFP as a natural antimicrobial agent applied in food additives or pharmaceutical ingredients.