The Phylogenomic Diversity of Herbivore-Associated<i>Fibrobacter</i>spp. Is Correlated to Lignocellulose-Degrading Potential

Abstract

The herbivore gut microbiome is incredibly diverse, and a functional understanding of this diversity is needed to more reliably manipulate this community for specific gain, such as increased production in ruminant livestock. Microbial degraders of plant cell wall polysaccharides in the herbivore gut, particularly Fibrobacter spp., are of fundamental importance to their hosts for digestion of a diet consisting primarily of recalcitrant plant fibers. Considerable phylogenetic diversity exists among members of the genus Fibrobacter , but much of this diversity remains cryptic. Here, we used comparative genomics, applied to a diverse collection of recently isolated Fibrobacter strains, to identify a robust association between carbohydrate-active enzyme gene content and the Fibrobacter phylogeny. Our results provide the strongest evidence reported to date for functional differences among Fibrobacter phylotypes associated with either the rumen or the hindgut and emphasize the general significance of carbohydrate-active enzymes in the evolution of fiber-degrading bacteria.