Is the CH4, H2 and CO venting from submarine hydrothermal systems produced by thermophilic bacteria?

• Published in: Nature (London) 1982-07, Vol.298 (5872), p.366-368
• Main Authors: Baross, John A., Lilley, Marvin D., Gordon, Louis I.
• Format: Article
• Language: English
• Subjects: Humanities and Social Sciences; letter; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/298366a0

Submarine hydrothermal vents are a major source of methane to the oceans 1,2 . The methane, as well as H 2 and CO, are generally believed to result from degassing of the mantle or from abiogenic water–rock reactions 1 , a conclusion supported by direct correlations between 3 He and CH 4 , and generally between CH 4 , H 2 and CO and dissolved silicate in hydrothermal waters 2,3 . An alternative source for these gases might be microbiological. This would imply that active bacterial communities exist in deep-sea hot water environments, some of which have temperatures exceeding 100 °C; this inference is without precedent. We have now found that the super-heated waters emanating from sulphide chimneys at 21 °N along the East Pacific Rise and samples from the sulphide chimneys themselves harbour complex communities of bacteria capable of growing with generation times of 37–65 min, producing CH 4 , CO, H 2 and traces of N 2 O in media containing S 2 O 2− 3 , Mn 2+ and Fe 2+ as energy sources, and oxidizing CH 4 , at 100 ± 2 °C at 1 atm. These microbial communities consist of three to five morphologically distinct types and include both oxidative and anaerobic species. These mixed cultures will not grow at temperatures below 70–75 °C. Even though some of the communities originated from water of temperatures >300 °C, it is not known if they can grow and produce CH 4 , CO and H 2 in super-heated waters kept liquid due to hydrostatic pressure. The discovery of these obligately thermophilic, gas-producing and consuming bacterial communities associated with submarine volcanic environments has interesting and important implications for prokaryotic evolution, marine geochemistry, industrial microbiology and exobiology.