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Rock‐crushing derived hydrogen directly supports a methanogenic community: significance for the deep biosphere
- Parkes, Ronald John, Berlendis, Sabrina, Roussel, Erwan G., Bahruji, Hasiliza, Webster, Gordon, Oldroyd, Anthony, Weightman, Andrew J., Bowker, Michael, Davies, Philip R., Sass, Henrik
- Environmental microbiology reports 2019 v.11 no.2 pp. 165-172
- aerobes, biosphere, earthquakes, granite, hydrogen, hydrogen production, mechanochemistry, methane, methane production, methanogens, microbial communities, oxidants, photosynthesis, potential energy
- Microbial populations exist to great depths on Earth, but with apparently insufficient energy supply. Earthquake rock fracturing produces H₂ from mechanochemical water splitting, however, microbial utilization of this widespread potential energy source has not been directly demonstrated. Here, we show experimentally that mechanochemically generated H₂ from granite can be directly, long‐term, utilized by a CH₄ producing microbial community. This is consistent with CH₄ formation in subsurface rock fracturing in the environment. Our results not only support water splitting H₂ generation as a potential deep biosphere energy source, but as an oxidant must also be produced, they suggest that there is also a respiratory oxidant supply in the subsurface which is independent of photosynthesis. This may explain the widespread distribution of facultative aerobes in subsurface environments. A range of common rocks were shown to produce mechanochemical H₂, and hence, this process should be widespread in the subsurface, with the potential for considerable mineral fuelled CH₄ production.