Genomic Characteristics Distinguish Geographically DistributedDehalococcoidia

Dehalococcoidia(Dia) class microorganisms are frequently found in various pristine and contaminated environments. Metagenome-assembled genomes (MAGs) and single-cell amplified genomes (SAGs) studies have substantially improved the understanding ofDiamicrobial ecology and evolution; however, an updated thorough investigation on the genomic and evolutionary characteristics ofDiamicroorganisms distributed in geographically distinct environments has not been implemented. In this study, we analyzed available genomic data to unravelDiaevolutionary and metabolic traits. Based on the phylogeny of 16S rRNA genes retrieved from sixty-seven genomes,Diamicroorganisms can be categorized into three groups, the terrestrial cluster that contains allDehalococcoidesandDehalogenimonasstrains, the marine cluster I, and the marine cluster II. These results reveal that a higher ratio of horizontally transferred genetic materials was found in theDiamarine clusters compared to that of theDiaterrestrial cluster. Pangenome analysis further suggests thatDiamicroorganisms have evolved cluster-specific enzymes (e.g., dehalogenase in terrestrialDia, sulfite reductase in marineDia) and biosynthesis capabilities (e.g., siroheme biosynthesis in marineDia). MarineDiamicroorganisms are likely adapted to versatile metabolisms for energy conservation besides organohalide respiration. The genomic differences between marine and terrestrialDiamay suggest distinct functions and roles in element cycling (e.g., carbon, sulfur, chlorine), which require interdisciplinary approaches to unravel the physiology and evolution ofDiain various environments.