Culture-Independent Species-Level Taxonomic and Functional Characterisation of Bacteroides, the Core Bacterial Genus Within Reptile Guts

The genus Bacteroides is a widespread and abundant bacterial taxon associated with gut microbiotas. Species within Bacteroides fill many niches, including as mutualists, commensals and pathogens for their hosts. Within many reptiles, Bacteroides is a dominant, ‘core’ gut bacterium that sometimes exhibits increased abundance in times of food scarcity, such as during hibernation. Here, we take a two-pronged approach to better characterise Bacteroides populations in reptile guts. Firstly, we leverage published 16S rRNA gene sequence datasets to determine the species-level distributions of Bacteroides members in reptile hosts. Secondly, we mine publicly available metagenomes to extract data for Bacteroides from reptiles, birds, amphibians and mammals, to compare the functional potential of Bacteroides in different host taxa. The 16S rRNA gene analyses revealed that B. acidifaciens is the most common Bacteroides species in reptile guts, and that different orders of reptiles differ in which Bacteroides species they harbour. The taxonomy of Bacteroides species recovered from metagenomic assembly did not differ between reptile orders or substantially across birds, amphibians and mammals. Metagenome-assembled genomes for Bacteroides species were marginally more related when their hosts were more closely related, with reptile hosts in particular harbouring markedly more unique Bacteroides MAGs compared to other hosts. Our findings indicate that hosts harbour similar profiles of Bacteroides species across broad comparisons, but with some differences between reptile groups, and that Bacteroides appears to perform largely similar roles in vertebrate host guts regardless of host relatedness.