Acetylene Fermentation: Primordial Biogeochemistry, the Search for Life in the Outer Solar System, and Maybe Some Earthly Bioremediation too.
Abstract
Acetylene (C2H2) fermentation was a serendipitous find of conducting C2H2-block assays of N2O reductase. Pelobacter acetylenicus grows on C2H2 via C2H2 hydratase (AH). AH is W-containing, exothermic, witha low redox potential. Unlike nitrogenase (N2ase), AH is specific for C2H2. When hydrated it forms acetaldehyde which is dismutated to ethanol, acetate providing energy plus carbon not only for P. acetylenicus but also for satellite anaerobes (e.g., sulfate-reducers, methanogens). But is there a larger significance to organisms that express AH? C2H2 is formed in the atmospheres of anoxic planet(oid)s by photolytic reactions of methane. Hence, the methane rich gas giants (e.g., Jupiter) and Titan have C2H2. It is also appears present in the Enceladus jets. Primordial Earth likely had a methane-rich atmosphere. Perhaps AH had a role in the evolution of primordial food chains in as much as C2H2 is easily metabolized when compared to methane? Akin to an ancient pablum for infant microbes that crawled out of the primordial soup. If so, it could also be a target substrate when searching for life on planet(oid)s of the outer Solar System. With regard to bioremediation, AH activity is relatively rare in assayed anoxic sediments. The exception was ground-waters contaminated with trichloroethylene (TCE), where dehalogenation gives rise to C2H2. Hence, there is an anthropogenic niche for pelobacter-like organisms in subsurface TCE-contaminated sites. Recent genomic sequencing suggests that P. acetylenicus contains not only AH, but N2ase as well, making it the only microbe that has the facility to metabolize C2H2 by either of the only two enzymes known that can achieve this feat. Both N2ase and AH are thought to be relic enzymes of Earth's transition from a pre-biotic to a biotic state where they were first employed to cleanse the primordial soup of nasty toxicants (e.g., cyanide). If so, why have they persisted, and what regulates their expression are questions we hope to address using our San Francisco Bay isolate, Pelobacter strain SFB93.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMOS52C..01O
- Keywords:
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- 0498 General or miscellaneous;
- BIOGEOSCIENCESDE: 4899 General or miscellaneous;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICALDE: 4599 General or miscellaneous;
- OCEANOGRAPHY: PHYSICAL