Project: Determination of deep biosphere cell activity and identity utilizing the state of the art low-biomass, single cell techniques developed at JAMSTEC in their class 10,000 clean room

IODP Expedition 337 set the record for deepest marine scientific drilling down to 2.4 kmbsf. This cruise also had the unique opportunity to retrieve deep cores from the Shimokita coal bed system in Japan with the aseptic and anaerobic conditions necessary to look for deep life. Onboard scientists prepared nearly 1,700 microbiology samples shared among five different countries to study life in the deep biosphere. Samples spanned over 1km in sampling depths and include representatives of shale, sandstone, and coal lithologies. Findings from previous IODP and deep mine expeditions suggest the genetic potential for methylotrophy in the deep subsurface, but it has yet to be observed in incubations. A subset of Expedition 337 anoxic incubations were prepared with a range of 13C-methyl substrates (methane, methylamine, and methanol) and maintained near in situ temperatures. To observe 13C methyl compound metabolism over time, we monitored the δ13C of the dissolved inorganic carbon and methane (by-products of methyl compound metabolism) over a period of 1.5 years. Our geochemical evidence suggests that the coal horizon incubated with 13C-methylamine showed the highest activity of all methyl incubations. Therefore, there are not only cells in the deeply buried terrigenous coal bed at Shimokita, but a microbial community that can be activated by methylotrophic compounds. Incubations showing the highest geochemical activity were prepared at the JAMSTEC Kochi Core Center for nanoSIMS analysis in March of 2015, and will be analyzed at Caltech in the coming months. This will allow us to observe if cells also incorporated the labeled methyl compounds into their body mass and provide another line of evidence that these substrates were used by the deep coalbed microbial community.