BioSciences

The global deep subsurface biosphere is thought to be one of the largest reservoirs for microbial life on our planet. This study takes advantage of new sampling technologies and couples them with improvements to DNA sequencing and associated informatics tools to reconstruct the genomes of uncultivated Bacteria and Archaea from fluids collected deep within the subseafloor of the Juan de Fuca Ridge. Here, we generated two metagenomes from borehole observatories located 311 meters apart and, using binning tools, retrieved 98 genomes from metagenomes (GFMs) with completeness > 10%. Of the GFMs, 31 were estimated to be > 90% complete, while an additional 17 were > 70% complete. In most instances, estimated redundancy in the GFMs was < 10%. Phylogenomic analysis revealed 53 bacterial and 45 archaeal GFMs and nearly all were distantly related to known cultivates. In the GFMs, abundant bacteria included Chloroflexi, Nitrospirae, Acetothermia (OP1), EM3, Aminicenantes (OP8), Gammaproteobacteria, and Deltaproteobacteria and abundant archaea included Archaeoglobi, Bathyarchaeota (MCG), and Marine Benthic Group E (MBG-E). In this study, we identified the first near-complete genomes from archaeal and bacterial lineages THSCG, MBG-E, and EM3 and, based on the warm, subsurface and hydrothermally-associated from which these groups tend to be found, propose the names, Geothermarchaeota, Hydrothermarchaeota, and Hydrothermae, respectively. The data set presented here are the first description of Juan de Fuca igneous basement microbial GFMs reported and will provide a platform by which one can perform a higher level interrogation of the many uncultivated lineages presented herein.