Isolation and Probiotic Functions of Bacillus subtilis and Its Inhibitory Effects on Colitis

Bacillus subtilis, as a probiotic feed additive, has been increasingly applied in livestock and poultry farming. In the present study, the environmental tolerance of a strain of Bacillus subtilis, isolated from a goat farm, was investigated. This article conducts a series of experiments on the obtained strains. The results demonstrated that the isolated strain exhibits strong tolerance to high temperatures, acidic and alkaline conditions, and high concentrations of bile salts. Furthermore, its self-aggregation rate exceeded 60% after 24 h. Whole-genome sequencing revealed that the genomes of the isolated strains were functionally annotated, identifying genes associated with amino acid metabolism, vitamin biosynthesis, and other metabolic pathways. Based on this genomic analysis, the present study further evaluated the anti-inflammatory effects of a Bacillus subtilis strain isolated in a murine model of colitis induced by dextran sulfate sodium (DSS). The analyses revealed that the DSS-treated group exhibited significantly reduced expression of intestinal tight junction proteins ZO-1 and Occludin, along with elevated expression of pro-inflammatory cytokines, compared to the PBS control group. Following oral administration of 1 × 10⁸ CFU/mL Bacillus subtilis isolated strain suspension, the DSS-treated mice showed increased expression of ZO-1 and Occludin and decreased levels of pro-inflammatory cytokines. These results indicate that the isolated strain of Bacillus subtilis has a protective effect against colitis and demonstrates probiotic potential.