Cloacimonadota metabolisms include adaptations for engineered environments that are reflected in the evolutionary history of the phylum

Abstract

Phylum Cloacimonadota (previously Cloacimonetes, WWE1) is an understudied bacterial lineage frequently associated with engineered and wastewater systems. Cloacimonadota members were abundant and diverse in metagenomic datasets from a municipal landfill, prompting an examination of phylogenetic relationships, metabolic diversity, and pangenomic dynamics across the phylum, based on 22 publicly available genomes and 24 from landfill samples. Cloacimonadota formed two discrete clades, with one clades genomes principally deriving from engineered systems. A few more-divergent genomes were placed basal in the tree, and not associated with either clade. Metabolic reconstructions for metagenome-assembled genomes predict an anaerobic, acetogenic, and fermentative lifestyle for the majority of Cloacimonadota surveyed. Genomes from engineered ecosystems (first clade) encode a unique suite of genes not typically found in genomes from natural environments (second clade). These encoded functions include acetate kinase, the enzyme responsible for the formation of acetate from acetyl phosphate, and carbon utilization enzymes, suggesting different substrate degradation and energy generation strategies in these ecologically and phylogenetically distinct lineages. Originality/Significance StatementCloacimonadota is a bacterial phylum that is under-described compared to its members prevalence in genome repositories. Cloacimonadota are frequently associated with engineered systems, including being identified as abundant and diverse in the municipal landfill site surveyed in this study. We reconstructed twenty-four landfill-associated Cloacimonadota metagenome assembled genomes (MAGs), more than doubling the number of publicly available Cloacimonadota genomes. We combined these MAGs with available reference genomes to predict major metabolic pathways and to describe the conserved features in the lifestyle of phylum Cloacimonadota. We found that Cloacimonadota have distinct evolutionary histories associated with engineered versus natural environments. Prior studies have evaluated metabolism from individual Cloacimonadota genomes - this work is the first to examine trait distribution across a more-complete representation of the phylum, including identification of genomic features and metabolic strategies that correlate to habitat of origin.