Evidence for a subsurface biosphere at deep-sea hydrothermal vents

1 Evidence for a subsurface biosphere at deep-sea hydrothermal vents Deming and Baross (1993) proposed the study of accessible black smokers and the ejecta of seafloor diking eruptive events (see below) as indirect windows to the subsurface. Since then, numerous studies have documented a variety of evidence supporting the existence of a subsurface biosphere below mid-ocean ridges, although the quantitative importance of this biosphere remains to be established (Kelley etal., 2002). 

Pathway Electron donor Electron acceptor Carbon source Reactions Examples of organisms and environments 

Hydrogen oxidation h2 02, possibly N03 co2 4H2 + 02 + C02 -4 [CH20] + 3H20 Mesophilic bacteria detected by activity measurements 

Metal oxidation Fe2+, Mn2+ 02, possibly NO s co2 2Fe2+ + 0.5O2 + 2H+ -4 2Fe3+ + H20 Mesophilic bacteria putative Gallionella, Leptothrix 

Nitrification NH4+, NOj- o2 co2, organic compounds nh3 + o2+co2 -4 [CH20]+HNOj Mesophilic bacteria Mevel etal. (1996) 

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