Microbial Diversity of Rock Surfaces on the 244 m Level of the Sanford Underground Research Facility at Different Spatial Scales — 8p — Caitlyn Lewis, Oxana Gorbatenko, Raine Flick, Abigail Domagall

The Sanford Underground Research Facility (SURF), previously the Homestake mine, provides an opportunity to investigate subterranean microbial life. Samples were collected from the 244 m level of SURF by gently pressing micropipette tips to the thin layer of sediment covering the rock walls of tunnels. Samples were collected from five sites 10 m apart, each consisting of five subsites within 1 m of each other with five samples less than 2 cm from each other. Samples contained up to 1 microliter sediment particles. Polymerase Chain Reaction (PCR) was used to make libraries of the V4-V5 region of the 16S rRNA genes, which were sequenced using an Illumina NextSeq device to determine microbial diversity. Numbers of sequencing reads per sample ranged from less than 10,000 to over one million. Because rare taxa may not be represented in the samples with low reads, samples with fewer than 100,000 reads were removed from the sample set. Common phyla found in samples were Proteobacteria, Actinobacteriota, Acidobacteriota, and Planctomycetota. Common genera included Pseudonocardia, Crossiella, Panacagrimonas, Sphingomonas, Polymorphobacter, and Lysobacter. The Chao 1 index indicates that not all probable Operational Taxonomic Units (OTUs or putative species) are represented in some samples. Principal Coordinate Analysis shows some clustering of samples within sites, but not within subsites, possibly due to differences in the geology among the five sites. The data shows how geology influences underground microbial diversity; however, more 16S rRNA gene sequencing is needed to provide better estimates of the richness of microbial genera and species.

Ohio University
Dave Bergmann