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Microbial life inhabits deeply buried marine sediments, but the extent of this vast ecosystem remains poorly constrained. Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan. Microbial methanogenesis was indicated by the isotopic compositions of methane and carbon dioxide, biomarkers, cultivation data, and gas compositions. Concentrations of indigenous microbial cells below 1.5 km ranged from <10 to ~10⁴ cells cm⁻³. Peak concentrations occurred in lignite layers, where communities differed markedly from shallower subseafloor communities and instead resembled organotrophic communities in forest soils. This suggests that terrigenous sediments retain indigenous community members tens of millions of years after burial in the seabed.

Source: http://dx.doi.org/10.1126/science.aaa6882

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Awards

Awards > Research Exchange Grants

Award Dates: March 17, 2015 — April 10, 2015

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

PI: Elizabeth Trembath-Reichert (California Institute of Technology)

Advisor: Victoria J. Orphan (California Institute of Technology)

Host: Fumio Inagaki (JAMSTEC)

Publications > Journal Article

Science

Evidence for Microbial Carbon and Sulfur Cycling in Deeply Buried Ridge Flank Basalt

Published: March 14, 2013

C-DEBI Contribution Number: 139

Abstract

Sediment-covered basalt on the flanks of mid-ocean ridges constitutes most of Earth’s oceanic crust, but the composition and metabolic function of its microbial ecosystem are largely unknown. By drilling into 3.5-million-year-old subseafloor basalt, we demonstrated the presence of methane- and sulfur-cycling microbes on the eastern flank of the Juan de Fuca Ridge. Depth horizons with functional genes indicative of methane-cycling and sulfate-reducing microorganisms are enriched in solid-phase sulfur and total organic carbon, host δ¹³C- and δ³⁴S-isotopic values with a biological imprint, and show clear signs of microbial activity when incubated in the laboratory. Downcore changes in carbon and sulfur cycling show discrete geochemical intervals with chemoautotrophic δ¹³C signatures locally attenuated by heterotrophic metabolism.

Source: http://dx.doi.org/10.1126/science.1229240

Person: M. Elvert

Abstract

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Abstract