Amino Acid-Derived Quorum Sensing Molecule Alanine on the Gastrointestinal Tract Tolerance of the Lactobacillus Strains in the Cocultured Fermentation Model.

More and more people are aware of the importance of intestinal flora to human health, and people are interested in the regulation of intestinal flora and its interaction with the host. The survival status of the probiotics in the gastrointestinal environment and the microbial interactions between the lactic acid bacteria have also received considerable attention. In this study, the gastrointestinal environment tolerance, adhesion ability, and biofilm formation of the Lactobacillus strain in the coculture system were explored through the real-time fluorescence-based quantitative PCR, UPLC-MS/MS metabolic profiling analysis, and Live/Dead BacLight cell staining methods. The results showed that the coculture system could promote the release of signal molecules autoinducer-2 and effectively protect the viability of the Lactobacillus acidophilus in the gastrointestinal environment. Meanwhile, amino acid-derived characteristic metabolite l-alanine (1%) could effectively enhance the communication of the cells in the complex fermentation model, which led to an increase in the tolerance ability of the L. acidophilus by 28% in the gastrointestinal-like environment. IMPORTANCE It was deduced from the study that amino acid-derived metabolites play an important role in cell communication in the gastrointestinal tract (GIT) environment, thus enhancing the communication of Lactobacillus strains in the complex fermentation model. Meanwhile, the viability of Lactobacillus acidophilus can be increased in the coculture system during the gastrointestinal stress environment treated with the amino acid-derived quorum sensing (QS) molecule l-alanine. It will shed some light on the application of amino acid-derived QS molecules in the fermentation stater industry.

Adhesion properties of cell surface proteins in Lactobacillus strains in the GIT environment.

As a broadly defined member of lactic acid bacteria (LAB), the Lactobacillus strain is well characterized in food fermentation and specific strains can enhance the intestinal barrier function and be recognized as the probiotic strain. In recent years, many molecules of the cell surface are thought to be related to the adhesion property in the gastrointestinal mucosa. Mucus layer-related proteins, extracellular matrix proteins, and immunoglobulins also exhibit immunity regulation and protection of the intestinal epithelial barrier function. Meanwhile, the effects of bile and the low pH of the gastrointestinal tract (GIT) on Lactobacillus colonization are also needed to be considered. Furthermore, LAB can adhere and aggregate in the GIT to promote the maturity of biofilm and the extracellular matrix secreting through the signal molecules in the quorum sensing (QS) system. Therefore, it is of great interest to use the QS system to regulate the initial adhesion ability of Lactobacillus and further enhance the probiotic effect of the biofilm formation of beneficial bacteria. This review summarizes the adhesion properties of cell surface proteins derived from Lactobacillus strains in recent studies and provides valuable information on the QS effect on the adhesion property of Lactobacillus strains in the GIT environment.

Changes of the mice intestinal microbes by the oligosaccharides-enriched fermented milk in a gender-dependent pattern.

Oligosaccharides are prebiotics that can be used to regulate microbes in the host intestine. In this study, we investigated the effects of different oligosaccharides on the changes of the intestinal microbial communities and co-related functional genes in the intestinal microbes. Fructo-oligosaccharide (FOS), galacto-oligosaccharide (GOS) and oligomannose (MOS) were enriched in milk and fermented by Lactobacillus plantarum and tested in ICR mice model in vivo. Then the changes of the fecal microbial communities were examined by 16S rDNA gene sequencing approach. We found that the relative abundance of several taxa was markedly different between genders at the level of phylum and genera, additionally to the changes in the microbial community. Meanwhile, compared with male mice, the intestinal microbes of the female mice group had significant changes. Furthermore, the intestinal microbial diversity was enhanced in the female mice when treated with the FOS enriched fermented milk. Therefore, this data suggests that oligosaccharides have the potential to improve the host microbial diversity in the intestinal tract, and FOS has potential applications in the fermented dairy industry. It revealed a gender-dependent changes of different oligosaccharides-enriched fermented milk on the intestinal microbes of mice, providing a reference for regulating the intestinal microbes by oligosaccharides.