Global landscape of gut microbiome diversity and antibiotic resistomes across vertebrates.

Multiple factors influence gut microbiome diversity in vertebrate hosts. Most previous studies have only investigated specific factors and certain host species or taxa. However, a comprehensive assessment of the relative contributions of individual factors towards gut microbial diversity within a broader evolutionary context remains lacking. Here, 2202 16S rRNA gene sequencing samples of gut bacterial communities collected from 452 host species across seven classes were analyzed together to understand the factors broadly affecting vertebrate gut microbiomes across hosts with different diets, threatened status, captivity status, and habitat environmental factors. Among wild vertebrates, diet was most significantly associated with gut microbiome alpha diversity, while host phylogeny and diet were significantly associated with beta diversity, consistent with a previous study. Host threatened status and habitat environmental factors (e.g., geography and climate) were also associated with gut bacterial community beta diversity. Subsequent ecological modeling revealed a strong association between stochastic assembly processes and patterns of gut bacterial diversity among free-ranging vertebrates. In addition, metagenomic analysis of gut microbiomes from 62 captive vertebrates and sympatric humans revealed similar diversity and resistome profiles despite differences in host phylogeny, diet, and threatened status. These results thus suggest that captivity diminishes the effects of host phylogeny, diet, and threatened status on the diversity of vertebrate gut bacterial communities. The most overrepresented antibiotic resistant genes (ARGs) observed in these samples are involved in resistance to ß-lactams, aminoglycosides, and tetracycline. These results also revealed potential horizontal transfers of ARGs between captive animals and humans, thereby jointly threatening public health and vertebrate conservation. Together, this study provides a comprehensive overview of the diversity and resistomes of vertebrate gut microbiomes. These combined analyses will help guide future vertebrate conservation via the rational manipulation of microbial diversity and reducing antibiotic usage.