Abstract

Along the eastern flank of the Juan de Fuca Ridge (JdFR), an array of boreholes drilled through sediments and into subseafloor basalt are fitted with CORKs (Circulation Obviation Retrofit Kits) that hydrologically seal off boreholes from sediment pore water and enable direct sampling of pristine basalt-hosted fluids. In this system, the members of the bacterial phylum Nitrospirae, which are closely related to the thermophilic anaerobic sulfate-reducing Thermodesulfovibrio, are among the most abundant bacteria. However, the metabolic and evolutionary profile of this microbe in this ridge system has yet to be fully elucidated. Here, we analyzed previously extracted and sequenced crustal fluid metagenomes from 2 CORKS (U1362A and U1362B) with total lengths of ~269Mbp and ~140Mbp, respectively, post quality control. The 2 metagenomes were assembled into scaffolds in metaSPades and assessed via read recruitment. Read recruitment results were further assessed, and visualized using a suite of programs in Anvi’o. Binning of scaffolds and subsequent manual refinement of bins were done based on the hierarchical clustering of tetra-nucleotide frequencies and GC content of scaffolds via the Anvi’o interactive and refine interface. Bins taxonomically identified as Nitrospirae using the GTDB-Tk classify workflow were placed in a separate Anvi’o collection, manually refined and assessed for completion and contamination using ‘–anvi-summarize’. Based on the preliminary analyses, we have identified seven bins in U1362A and 2 bins in U1362B belonging to the Nitrospirae phylum. All JdFR Nitrospirae bins have >50% completion and <5% redundancy. Also, the presence of two distinct GC contents (~40% vs 60%) of Nitrospirae may suggest that different populations exist within and between samples.