The appropriate dose of Bacillus cereus improves the homeostasis of intestinal microbiota but does not significantly influence microbial functions in Paramisgurnus dabryanus

Abstract

The intestinal microbiota play a vital role in the growth and health of the host. Probiotics could influence the homeostasis of intestinal microbiota, but the relationship between species and ecosystem stability is poorly understood. Here, four diets with different doses of Bacillus cereus (control, 0 cfu/kg; BL7, 107 cfu/kg; BL9, 109 cfu/kg; and BL11, 1011 cfu/kg) were designed to investigate the intestinal microbiota in Paramisgurnus dabryanus. The growth experiment demonstrated that the growth performance and the indices of Chao1, phylogenetic diversity, Simpson and Shannon improved significantly after loaches were fed a BL11 diet. The dominant composition of intestinal microbiota at phylum, class and genus levels did not change in loach after feeding different diets. Categories of bacterial taxa revealed that rare taxa and conditionally rare taxa were the dominant bacterial taxa in intestinal microbiota of loach. B. cereus supplemented with 1011 cfu/kg promoted the stability of the ecological network of intestinal microbiota by reinforcing the cooperation of interspecific interactions, promoting operational taxonomic units to shape larger submodules and increasing module hubs species and connectors species. Results of functional prediction revealed that a total of 5692 functions were shared among the four groups, which accounted for 91.7% of overall functions. To sum up, dietary supplementation with B. cereus had no significant influences on the composition and bacterial taxa of intestinal microbiota and the composition of bacterial functions. A dose of B. cereus appropriate to the diet could improve the growth performance and promote the homeostasis of intestinal microbiota in loach.