Response of Salmonella enterica serovar Typhimurium to alginate oligosaccharides fermented with fecal inoculum: integrated transcriptomic and metabolomic analyses

Abstract

Alginate oligosaccharides (AOS), extracted from marine brown algae, are a common functional feed additive; however, it remains unclear whether they modulate the gut microbiota and microbial metabolites. The response of Salmonella enterica serovar Typhimurium, a common poultry pathogen, to AOS fermented with chicken fecal inocula was investigated using metabolomic and transcriptomic analyses. Single-strain cultivation tests showed that AOS did not directly inhibit the growth of S. Typhimurium. However, when AOS were fermented by chicken fecal microbiota, the supernatant of fermented AOS (F-AOS) exhibited remarkable antibacterial activity against S. Typhimurium, decreasing the abundance ratio of S. Typhimurium in the fecal microbiota from 18.94 to 2.94%. Transcriptomic analyses showed that the 855 differentially expressed genes induced by F-AOS were mainly enriched in porphyrin and chlorophyll metabolism, oxidative phosphorylation, and Salmonella infection-related pathways. RT-qPCR confirmed that F-AOS downregulated key genes involved in flagellar assembly and the type III secretory system of S. Typhimurium, indicating metabolites in F-AOS can influence the growth and metabolism of S. Typhimurium. Metabolomic analyses showed that 205 microbial metabolites were significantly altered in F-AOS. Among them, the increase in indolelactic acid and 3-indolepropionic acid levels were further confirmed using HPLC. This study provides a new perspective for the application of AOS as a feed additive against pathogenic intestinal bacteria.

Potential Application of Marine Fucosyl-Polysaccharides in Regulating Blood Glucose and Hyperglycemic Complications

“…As a result, researchers are increasingly looking to find alternative sources of natural resource-based glycemic drugs to delay hyperglycemic complications, mitigate side effects and reduce costs [ 4 , 7 ]. In recent years, with the development and utilization of marine biological resources, some active ingredients isolated from marine organisms, such as marine polysaccharides, have been proved to have the effects of lowering blood pressure/glucose/lipid, anticoagulant and immune regulation, thus attracting widespread attention [ 27 , 28 , 29 , 30 , 31 ]. Marine fucosyl-polysaccharides extracted from algae and sea cucumbers are a kind of fucose-containing sulphated polysaccharide.…”