Non-negligible role of gut morphology in shaping mammalian gut microbiomes.

Because of the overemphasis on the roles of diet and phylogeny in shaping the gut microbiome, the gut morphology is seldom independently considered and even often ignored. To address this research gap, we investigated a large-scale dataset of mammalian gut microbiomes, comprising 16S ribosomal RNA and metagenomic sequencing data from 292 species spanning 20 orders. We dissected the effects of various factors on the gut microbiome across four distinct gut morphology categories (foregut/hindgut/simple, foregut/hindgut, functional ruminant/ruminant-like, and colon fermenter/cecum fermenter) and uncovered the synergistic effect between phylogeny and gut morphology. Moreover, we identified the significant role of gut morphology in the gut microbiomes of hosts occupying specific niches, as well as those within the same taxonomic order but with different gut morphologies. We also identified three enterotype indices-Fusobacterium, UCG-005, and Prevotella-which could predict the three gut morphology types of mammals: simple, foregut, and hindgut. These findings enhance our understanding of mammalian gut microbial assembly and provide novel insights into host-microbe coevolution.