Hydrogen cycle

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Hydrogen is one of the constituents of water. It recycles as in other biogeochemical cycles. It is actively involved with the other cycles like the carbon cycle, nitrogen cycle, sulfur cycle and oxygen cycle as well.

Anaerobic fermentation of organic substances to carbon dioxide and methane is a collaborative effort involving many different biochemical reactions, processes and species of microorganisms. One of these many processes that occur is termed "interspecies hydrogen transfer". This process has been described as integral to the symbiosis between certain methane-producing bacteria (methanogens) and nonmethanogenic anaerobes. In this symbiosis, the nonmethanogenic anaerobes degrade the organic substance and produce -among other things- molecular hydrogen (H₂). This hydrogen is then taken up by methanogens and converted to methane via methanogenesis. One important characteristic of interspecies hydrogen transfer is that the H₂ concentration in the microbial environment is very low. Maintaining a low hydrogen concentration is important because the anaerobic fermentative process become increasingly thermodynamically unfavorable as the partial pressure of hydrogen increases. a key difference compared to other biogeochemical cycles is that because of its low molecular weight hydrogen can leave Earth's atmosphere. It has been suggested that this occurred on a grand scale in the past and that this is why today the Earth is mostly irreversibly oxidised.^[1]

References

^ http://www.sciencemag.org/cgi/content/abstract/293/5531/839 Biogenic Methane, Hydrogen Escape, and the Irreversible Oxidation of Early Earth David C. Catling, Kevin J. Zahnle, and Christopher McKay (3 August 2001) Science 293 (5531), 839. [DOI: 10.1126/science.1061976]

External links

A Lecture

Bibliography

"Microbiology and Biochemistry of Strict Anaerobes Involved in Interspecies Hydrogen Transfer" by Jean-Pierre Bélaich; Mireille Bruschi; Jean-Louis Garcia; Federation of European Microbiological Societies. Published Nov 1990. ISBN 0306435179
[1] F.A.M. de Bok, C.M. Plugge, and A.J.M. Stams; "Interspecies eletron transfer in methanogenic proprionate degrading consortia". Water Research 38 (2004): 1368-1375
[2] A.J.M. Stams et al., "Exocellular electron transfer in anaerobic microbial communities", Environmental Microbiology, 8 (2006):371-382

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[1] ttp://www.sciencemag.org/cgi/content/abstract/293/5531/839 Biogenic Methane, Hydrogen Escape, and the Irreversible Oxidation of Early Earth David C. Catling, Kevin J. Zahnle, and Christopher McKay (3 August 2001) Science 293 (5531), 839. [DOI: 10.1126/science.1061976]

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v t e Biogeochemical cycles
Cycles	Carbon cycle carbonate–silicate cycle deep carbon cycle oceanic carbon cycle Chlorine cycle Hydrogen cycle Iron cycle Mercury cycle Mineral cycle Nitrogen cycle Nutrient cycle Oxygen cycle ozone Phosphorus cycle Rock cycle Selenium cycle Silica cycle Sulfur cycle Water cycle deep water cycle Marine biogeochemical cycles
Research groups	DAAC GEOTRACES IMBER NOBM SOLAS
Related topics	Biogeochemistry geochemical cycle chemical cycling environmental chemistry Biosequestration carbon sequestration carbon sink soil carbon biological pump viral shunt mycorrhizal fungi Ocean acidification acid rain Methane clathrate clathrate gun hypothesis Arctic methane emissions Human impact on the nitrogen cycle Lichens and nitrogen cycling Nitrification Nitrogen fixation Nitrogen assimilation Phosphorus assimilation Sulfur assimilation Planetary boundaries
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