Genomic Characteristics Distinguish Geographically Distributed .

() 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 of microbial ecology and evolution; however, an updated thorough investigation on the genomic and evolutionary characteristics of microorganisms distributed in geographically distinct environments has not been implemented. In this study, we analyzed available genomic data to unravel evolutionary and metabolic traits. Based on the phylogeny of 16S rRNA genes retrieved from sixty-seven genomes, microorganisms can be categorized into three groups, the terrestrial cluster that contains all and strains, the marine cluster I, and the marine cluster II. These results reveal that a higher ratio of horizontally transferred genetic materials was found in the marine clusters compared to that of the terrestrial cluster. Pangenome analysis further suggests that microorganisms have evolved cluster-specific enzymes (e.g., dehalogenase in terrestrial , sulfite reductase in marine ) and biosynthesis capabilities (e.g., siroheme biosynthesis in marine ). Marine microorganisms are likely adapted to versatile metabolisms for energy conservation besides organohalide respiration. The genomic differences between marine and terrestrial may suggest distinct functions and roles in element cycling (e.g., carbon, sulfur, chlorine), which require interdisciplinary approaches to unravel the physiology and evolution of in various environments.