Genomes of Novel Reveal Severely Curtailed Machineries for Predation and Cellular Differentiation.

Cultured are predominantly aerobic soil inhabitants, characterized by their highly coordinated predation and cellular differentiation capacities. Little is currently known regarding yet-uncultured from anaerobic, nonsoil habitats. We analyzed genomes representing one novel order (o__JAFGXQ01) and one novel family (f__JAFGIB01) in the from an anoxic freshwater spring (Zodletone Spring) in Oklahoma, USA. Compared to their soil counterparts, anaerobic possess smaller genomes and a smaller number of genes encoding biosynthetic gene clusters (BGCs), peptidases, one- and two-component signal transduction systems, and transcriptional regulators. Detailed analysis of 13 distinct pathways/processes crucial to predation and cellular differentiation revealed severely curtailed machineries, with the notable absence of homologs for key transcription factors (e.g., FruA and MrpC), outer membrane exchange receptor (TraA), and the majority of sporulation-specific and A-motility-specific genes. Further, machine learning approaches based on a set of 634 genes informative of social lifestyle predicted a nonsocial behavior for Zodletone . Metabolically, Zodletone genomes lacked aerobic respiratory capacities but carried genes suggestive of fermentation, dissimilatory nitrite reduction, and dissimilatory sulfate-reduction (in f_JAFGIB01) for energy acquisition. We propose that predation and cellular differentiation represent a niche adaptation strategy that evolved circa 500 million years ago (Mya) in response to the rise of soil as a distinct habitat on Earth. The phylum is a phylogenetically coherent bacterial lineage that exhibits unique social traits. Cultured are predominantly aerobic soil-dwelling microorganisms that are capable of predation and fruiting body formation. However, multiple yet-uncultured lineages within the have been encountered in a wide range of nonsoil, predominantly anaerobic habitats, and the metabolic capabilities, physiological preferences, and capacity of social behavior of such lineages remain unclear. Here, we analyzed genomes recovered from a metagenomic analysis of an anoxic freshwater spring in Oklahoma, USA, that represent novel, yet-uncultured, orders and families in the . The genomes appear to lack the characteristic hallmarks for social behavior encountered in genomes and displayed a significantly smaller genome size and a smaller number of genes encoding biosynthetic gene clusters, peptidases, signal transduction systems, and transcriptional regulators. Such perceived lack of social capacity was confirmed through detailed comparative genomic analysis of 13 pathways associated with social behavior, as well as the implementation of machine learning approaches to predict social behavior based on genome composition. Metabolically, these novel are predicted to be strict anaerobes, utilizing fermentation, nitrate reduction, and dissimilarity sulfate reduction for energy acquisition. Our results highlight the broad patterns of metabolic diversity within the yet-uncultured and suggest that the evolution of predation and fruiting body formation in the has occurred in response to soil formation as a distinct habitat on Earth.