The gut microbiomes of 180 species

Microbial life is ubiquitous in most environments on Earth, including in the gastrointestinal tract of animals. The composition of these collections of microbes, called the microbiota, can differ dramatically between individuals and species. Across the animal tree of life, these microbiotas contain a broad array of microbial diversity. Animal gut microbiota composition is more similar when hosts share diet or genetic ancestry, especially in mammals; the correlation of microbiota composition with genetic ancestry is weaker in fish, reptiles, birds, and invertebrates (1–4). In many cases, gut microbes contribute to key host processes, including metabolizing specialized dietary compounds (5). On page 264 of this issue, Levin et al. (6) interrogate the microbes that inhabit the animal gut by sequencing fecal samples from ∼180 wild and captive species across the animal tree of life. Most of the bacterial species and genes they found have not been described before.