Metagenomics analysis yields assembled genomes from prokaryotic anaerobes with polymer-degrading potential

Anaerobic microbial communities are often highly degradative, such as those found in the herbivore rumen and large-scale anaerobic digesters. Since the microbial communities in these systems degrade recalcitrant organic polymers, we hypothesize that some microbes in anaerobic environments may be involved in man-made plastic association, deformation, or even breakdown. While efforts have been put toward characterizing microbial communities, many microbes remain unidentified until they can be sufficiently cultivated to generate enough genetic material to assemble high-quality metagenome assemblies and reference genomes. In this study, microbial consortia from goat fecal pellets and anaerobic digester sludge were cultivated for over 6 weeks to assemble metagenomes from novel anaerobic taxa with potential degradative activity. To select for microbes with potential plastic-degrading abilities, plastic strips were included in culture, though the presence of plastic did not appear to enrich for particularly degradative consortia, yet it did select for novel species that otherwise may not have been characterized. Whole-genome shotgun sequencing enabled assembly of 72 prokaryotic metagenome-assembled genomes (MAGs) with >90% completion, <5% contamination, and an N50 >10,000 bp; 17 of these MAGs are classified as novel species given their lack of similarity to publicly available genomes and MAGs. These 72 MAGs vary in predicted carbohydrate-degrading abilities, with genes predicted to encode fewer than 10 or up to nearly 400 carbohydrate-active enzymes. Overall, this enrichment strategy enables characterization of less abundant MAGs in a community, and the MAGs identified here can be further mined to advance understanding of degradative anaerobic microbial consortia.