This project aimed to increase our understanding of the diversity, genomic potential, and activity of microbes living in three samples from deep subsurface oceanic crust located at Integrated Ocean Drilling Program (IODP) Site U1374, Rigil Guyot of the Louisville Seamount Chain. We sought to integrate three approaches to analyzing microbial diversity by sequencing whole community DNA, genomic DNA from single sorted cells, and actively transcribed genes from the whole community. The integrated analysis of these three datasets from the same sample provides a complimentary picture of subsurface microbiology whose net worth is far greater than the sum of its parts. Attempts to sort single cells from subsurface volcanic basement proved to be too difficult, however, and ultimately failed after multiple attempts. Despite this, we advanced understanding of how to approach single cell genomics with basement samples, and were able to photograph particles sorted with a flow cytometer, which revealed the apparent presence of spores and non-biogenic material. Given the difficulties encountered with the basement samples, we switched our focus to use the same methodology with microbial mats that form at diffuse venting sites along the Mid-Atlantic Ridge. Samples from Rainbow and TAG hydrothermal fields were sorted and 30 single cell genomes and one isolate genome were analyzed, targeting Zetaproteobacteria and understudied genera common to hydrothermal microbial mats, including 3 GNO2, 5 Chlorobi, 2 Methylococcales and 6 Gammaproteobacteria believed to be methylotrophs. In parallel, a metagenome and metatranscriptome was analyzed from the same TAG sample as the single cell genomes, as well as three other MAR metagenomes and one paired metatranscriptome. Analysis is underway and will target microbial understanding food web interactions in these subsurface derived mats.