Mantle degassing of primordial helium through submarine ridge flank basaltic basement

It is generally accepted that diverse, poorly characterized microorganisms reside deep within Earth’s crust. One such lineage of deep subsurface-dwelling bacteria is an uncultivated member of the Firmicutes phylum that can dominate molecular surveys from both marine and continental rock fracture fluids, sometimes forming the sole member of a single-species microbiome. Here, we reconstructed a genome from basalt-hosted fluids of the deep subseafloor along the eastern Juan de Fuca Ridge flank and used a phylogenomic analysis to show that, despite vast differences in geographic origin and habitat, it forms a monophyletic clade with the terrestrial deep subsurface genome of “Candidatus Desulforudis audaxviator” MP104C. While a limited number of differences were observed between the marine genome of “Candidatus Desulfopertinax cowenii” modA32 and its terrestrial relative that may be of potential adaptive importance, here it is revealed that the two are remarkably similar thermophiles possessing the genetic capacity for motility, sporulation, hydrogenotrophy, chemoorganotrophy, dissimilatory sulfate reduction, and the ability to fix inorganic carbon via the Wood-Ljungdahl pathway for chemoautotrophic growth. Our results provide insights into the genetic repertoire within marine and terrestrial members of a bacterial lineage that is widespread in the global deep subsurface biosphere, and provides a natural means to investigate adaptations specific to these two environments.

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Metagenome sequencing and 98 microbial genomes from Juan de Fuca Ridge flank subsurface fluids

10.7287/peerj.preprints.2613v1 ◽

2016 ◽

Author(s):

Sean P Jungbluth ◽

Jan P Amend ◽

Michael S Rappé

Keyword(s):

Juan De Fuca Ridge ◽

Phylogenomic Analysis ◽

Data Set ◽

Microbial Life ◽

Fuca Ridge ◽

Juan De Fuca ◽

Metagenome Sequencing ◽

The Many ◽

Ridge Flank ◽

Informatics Tools

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.

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