Study on Mechanism of GOS Promoting the Beneficial Function of Lactiplantibacillus Plantarum

The gut microbiome is affecting the behavior and health of the host with little effort. Probiotics are in the "frontal battlefield" of contact with intestinal microbes, so it is vitally important to study the interaction between probiotics and intestinal microbes. However, the competition between probiotics and intestinal symbiotic microbes is particularly fierce for limited nutrients and niche. Under the pressure of intestinal selection, both probiotics and intestinal symbiotic microbes will show Darwin mutation (also known as positive selection and adaptive mutation) to adapt to the new intestinal environment to varying degrees. In order to better regulate the colonization of probiotics in the intestinal tract of the host, nutritional support is gradually formed by supplementing prebiotics. However, prebiotics are not a specific nutrient of probiotics, and the synergistic process of prebiotics to probiotics in vivo is very lacking. In view of the above situation, the authenticity and potential mechanism of prebiotics promoting the colonization of probiotics in the gut of the host should be fully demonstrated. Secondly, it is necessary to prove the effectiveness of probiotics supplementation in promoting probiotics to play beneficial effects. Therefore, considering in intestinal ecology and evolution, a study took Lactiplantibacillus plantarum HNU082 (HNU082), a candidate probiotic isolated from traditional fermented food in Hainan, China, which has been widely confirmed to have potential beneficial function. The mechanism of promoting probiotics by prebiotics was studied by optimal prebiotics screening in vitro and animal experiment in vivo.

Firstly, the carbohydrate active enzymes composition and oligosaccharide utilization genes of HNU082 were annotated according to its genome, and a variety of oligosaccharides including galactooligosaccharides (GOS) were identified as candidate prebiotics. The optimal prebiotics of HNU082 were determined by liquid culture in vitro, growth curve, viable count and generation time, and then HNU082 and GOS were combined into complementary synbiotic. Next, the annotated analysis process of genetic variation of host intestinal microbes was established. Finally, it was confirmed that the abundance of HNU082 on host intestinal was obviously dependent on the supplementation of GOS. The differences single nucleotide variants located in strain adhesion protein between probiotics group and probiotics with continuous supplement GOS group, which supporting GOS changed the strain of adaptive evolution strategy, with less complete genome mutations to maximize colonization. Next, it was found that probiotics and continuous GOS supplementation changed the intestinal microbe’s composition to a minimum. The negative correlation between HNU082 and Bacteroides in the probiotic group turned to a positive one in the continuous GOS-supplementation group, indicating that the supplementation of GOS changed the ecological relationship between probiotics and intestinal symbiotic microbes, and improved the overall functional capacity related to the utilization of GOS. Finally, it was revealed that whether GOS supplementation or not did not affect the overall change of the genetic diversity of the local intestinal microbiota (mainly Bacteroides) during the consumption of probiotics, and the real core factor was exogenous probiotics.

In conclusion, the study confirmed that GOS assisted Lactiplantibacillus plantarum to achieve maximum stable colonization with minimal adaptive mutations. In order to minimize the shaking of the intestinal microbes as the basis, change the intestinal ecological network, coordinate the competitive symbiotic microorganisms (Bacteroides) to cooperative utilization of carbon sources, and maintain the adaptive evolution rate of Bacteroides on the premise of not increasing the intestinal selection pressure.