The Difference of the Composition and Digestive Enzymes of Gut Microbiome in Herbivorous Blunt Snout Bream (megalobrama Amblycephala) and Carnivorous Largemouth Bass (micropterus Salmoides)

Blunt snout bream (Megalobrama amblycephala) and largemouth bass (Micropterus salmoides) are a herbivorous and a carnivorous freshwater fish species respectively. These fish possess distinct intestinal microorganisms and digestive enzymes that play a vital role in nutrient digestion. As a result, herbivorous and carnivorous fish exhibit significant differences in their digestive strategies. In this study, we investigated the compositions and functions of the gut flora of herbivorous M. amblycephala and carnivorous M. salmoides by 16S rRNA sequencing. PCoA analysis revealed that the gut flora of M. amblycephala and M. salmoides formed two distinct clusters. OTU analysis found that M. amblycephala and M. salmoides shared a small number, but high abundance, of core microorganisms, and that a large number of microorganisms differed at the phylum and genus levels between the two species. The cellulose-degrading bacteria Longivirga, Flavobacterium, Clostridium_sensu_stricto_12, and Bacillus were dominant in M. amblycephala, while protein-degrading bacteria Clostridium_sensu_stricto_1, Lactococcus, Streptococcus and Proteiniclasticum were dominant in M. salmoides. PICRUSt analysis showed significant differences in carbohydrate and protein metabolism functions as well. In addition, cellulase and amylase activities were significantly higher in M. amblycephala than in M. salmoides, while trypsin activity was significantly higher in M. salmoides than in M. amblycephala. These results indicated that dietary patterns influenced the composition and function of the bacterial community and the activity of digestive enzymes in the host’s gut.