16S rRNA gene amplicon sequencing of the deep hydrothermally altered subsurface of a semi-arid environment (Chilean Coastal Cordillera)

Microbial mineral weathering has been predominantly investigated at shallow depths in humid and tropical environments. Here, the microbial community in the deep hydrothermally altered subsurface (ca. 77m depth, inside of aseptically crushed rocks, in-situ) of a semi-arid environment at the Chilean Coastal Cordillera and an enrichment culture thereof was investigated. The aim of the study was to obtain and investigate an Fe(III)-reducing enrichment culture originating from the deep subsurface to identify energy sources and mirobial key players in the weathering of Fe-bearing minerals in that environment. An anoxic mineral medium was amended with ferrihydrite (Fh) as an Fe(III) source and either (1 - ac) sodium acetate, or (2 - lc) sodium lactate, or (3 - h2) H2, or (4 - aclc) a mix of sodium acetate and sodium lactate as an electron donor for Fe(III) reduction. Microbial 16S rRNA genes were amplified using primers 515F and 806R targeting the V4 region, and subsequently library preparation with Nextera 2nd step PCR and sequencing on Illumina MiSeq were performed. The in-situ sample was sequenced with PE300 (v3) and enrichment cultures with PE250 (v2) chemistry. The sequencing data files here represent either primer-trimmed reads (in-situ) or raw data without any trimming, i.e. including primers (enrichments).