title: Evidence for microbial carbon and sulfur cycling in deeply buried ridge flank basalt.
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 δ(13)C- and δ(34)S-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 δ(13)C signatures locally attenuated by heterotrophic metabolism.
authors.affiliation: Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. mark.lever@biology.au.dk
authors.forename: Mark A
authors.initials: MA
authors.lastname: Lever
authors.forename: Olivier
authors.initials: O
authors.lastname: Rouxel
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Alt
authors.forename: Nobumichi
authors.initials: N
authors.lastname: Shimizu
authors.forename: Shuhei
authors.initials: S
authors.lastname: Ono
authors.forename: Rosalind M
authors.initials: RM
authors.lastname: Coggon
authors.forename: Wayne C
authors.initials: WC
authors.lastname: Shanks
authors.forename: Laura
authors.initials: L
authors.lastname: Lapham
authors.forename: Marcus
authors.initials: M
authors.lastname: Elvert
authors.forename: Xavier
authors.initials: X
authors.lastname: Prieto-Mollar
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Hinrichs
authors.forename: Fumio
authors.initials: F
authors.lastname: Inagaki
authors.forename: Andreas
authors.initials: A
authors.lastname: Teske
mesh_terms: D001483:Base Sequence; D002244:Carbon / Q000378:metabolism*; D008697:Methane / Q000378:metabolism*; D017018:Methanomicrobiales / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D019640:Methanosarcinales / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017640:Silicates; D013455:Sulfur / Q000378:metabolism*
chemical_list: D017640:Silicates; C060346:basalt; D013455:Sulfur; D002244:Carbon; D008697:Methane