Study on the promotive effect and mechanism of exogenous nucleotides on Lactobacillus casei antagonism against Salmonella enterica by coculture

Nucleotides (NTs) are extremely important low-molecular-weight compounds in organisms, and play an important role in cell metabolism, energy and functional regulation. Our previous study found that NTs regulated the intestinal flora of rapid-aging mice (senescence-accelerated mouse prone-8, SAMP-8) and played a significant role in promoting the growth of Lactobacillus casei. However, the mechanism by which NTs promote the antagonization of intestinal pathogens by probiotics remains unclear. Therefore, we explored the mechanism by which NTs promote the antagonization of intestinal pathogens by L. casei via in vitro coculture. The results showed that NTs promoted the growth of L. casei, while negatively affecting Salmonella enterica. NTs increased the antagonism of S. enterica biofilm formation, swimming, swarming, and secretion of siderophore by L. casei. This antagonism was probably due to NTs activating the LuxS protein in L. casei, which closely combines with NTs, promoting the secretion of AI-2 signaling molecule and triggering the expression of genes related to the quorum sensing system, enabling L. casei to produce specific physiological activities. This study provides a theoretical basis for exploring using NTs as potential prebiotics.