Ocean crust Targeted Locus (Loci)

Sampling

Much of the earth''s microbial biomass exists in the subsurface, and a sizable fraction of this is in oceanic igneous rocks. If microbial life in the igneous ocean crust extends to the depth of the ~120C isotherm (the current upper temperature limit of life) then the volume of rock available for microbial colonization is about the same as the volume of the oceans. Most of this volume is difficult to sample but microorganisms have been identified from deep layers of the igneous ocean crust. Additional understanding of the deep igneous biome comes from microorganisms extracted from subsurface fluids; although unattached microorganisms in aquifer fluids are not necessarily representative of the microorganisms attached to the host rocks. Another difficulty is that the ocean crust is mineralogically heterogeneous typically on the 0.01 mm to 10 mm scale and if the mineralogy influences or controls the microbial communities, then the ocean crust is microbially heterogeneous on the 0.01 to 10 mm scale. Community structure that is determined from bulk crustal rock samples will not be informative about how communities are associated with crustal minerals. Also, molecular and sample processing methods are not currently available to determine the community structure of minerals in igneous rocks. In situ colonization of mono-mineralic substrates in the ocean crust is one method of determining microbial community structure of the minerals that make up the crust. We devised a method of incubating a wide variety of mono-mineral aggregates in the ocean floor simultaneously so that they all experienced the same temperature, water composition, and pressure. The mass of each incubated mineral was large enough to expect recovery of adequate amounts of DNA for analysis. The location chosen for this experiment was Integrated Ocean Drilling Program (IODP) borehole 1301A, which is located at 47 45.210'' N, 127 45.833'' W in 3.6 Ma old ocean crust in the northeast Pacific Ocean.

Method steps

1. Pipeline used: https://www.ebi.ac.uk/metagenomics/pipelines/4.1