Abstract
Several Bacillus strains exert beneficial effects on the maintenance of intestinal homeostasis and host health. However, whether Bacillus amyloliquefaciens (BA) can improve gut microbial dysbiosis and ameliorate colitis is unknown. Therefore, we conducted the present study to investigate the effects of BA administration on intestinal morphology, inflammatory response, and colonic microbial composition in a mouse model of dextran sulfate sodium (DSS)-induced colitis. Results showed that BA administration significantly ameliorated body weight loss, decreased disease activity index, and improved colonic tissue morphology in DSS-treated mice. In addition, levels of immunoglobulins, as well as pro-inflammatory cytokines, were decreased after BA administration. Importantly, colonic microbiota profiling indicated a significant (p < 0.05) difference in beta-diversity between BA-administrated and DSS-treated mice, according to weighted principal coordinate analysis (PCoA) results. The relative abundance of the Firmicutes genus was increased, whereas that of Bacteroidetes was decreased by BA administration. Furthermore, phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) analysis showed that the most significantly changed pathways between the four groups of mice were carbohydrate, lipid, and amino acid metabolism. In conclusion, our results showed that BA administration has beneficial effects on DSS-induced colitis, suggesting that this strategy might be useful for the treatment of dysbiosis during ulcerative colitis. Further, the changes in metabolism, especially amino acid metabolism, might contribute to the beneficial effects of BA on the amelioration of DSS-induced colitis.
Highlights
Inflammatory bowel disease (IBD) is a chronic inflammatory disease that mostly occurs in the rectal and colonic mucosa and even deeper layers of the intestinal wall
Animals were randomly assigned into four groups as follows: mice were untreated for 7 days and orally gavaged PBS for 7 days (Control group); mice were supplemented with 3.5% dextran sulfate sodium (DSS) (w/v; molecular mass = 6,500–10,000 Da; Sigma-Aldrich, Shanghai, China) dissolved in fresh running water ad libitum for 7 days and orally gavaged PBS for 7 days (DSS group); mice were supplemented with 3.5% DSS for 7 days and orally gavaged B. amyloliquefaciens (1.0 × 108 CFU/kg in 200 μL of PBS/mouse/day) for 7 days (BaL group); mice were supplemented with 3.5% DSS for 7 days and orally gavaged with B. amyloliquefaciens (1.0 × 109 CFU/kg in 200 μL of PBS/mouse/day) for 7 days (BaH group)
Bacillus amyloliquefaciens have been widely used in animal feed as an alternative to antibiotics and no side effects were have previously been reported (Cao et al, 2018)
Summary
Inflammatory bowel disease (IBD) is a chronic inflammatory disease that mostly occurs in the rectal and colonic mucosa and even deeper layers of the intestinal wall. Emerging evidence has suggested that Bacillus amyloliquefaciens (BA) is beneficial for the amelioration of diarrhea and inflammation (Li et al, 2018). One study reported the beneficial effects of BA on IBD as it ameliorated the body weight loss of dextran sulfate sodium salt (DSS)-induced colitis animals, in addition to reducing the protein and mRNA levels of pro-inflammatory cytokines in colonic tissues (Hairul Islam et al, 2011). They did not report any related mechanisms including whether BA supplementation affected the composition of the gut microbiota
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