Biology
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p53d..03z&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #P53D-03
Biology
0406 Astrobiology And Extraterrestrial Materials, 0424 Biosignatures And Proxies, 0454 Isotopic Composition And Chemistry (1041, 4870), 0461 Metals, 1041 Stable Isotope Geochemistry (0454, 4870)
Scientific paper
The triple isotopes of oxygen (Δ17O' = δ17O'-0.528 × δ18O' using logarithmic deltas) can trace the oxygen sources of sulfate produced during sulfide oxidation, an important biogeochemical process on Earth's surface and possibly also on Mars [1]. δ18OSO4 compositions are determined by the isotopic selectivity of the mechanism(s) responsible for their changes, and the δ18O value of the reactants (O2 vs. H2O). The relative proportional importance and contribution of each of those sources and mechanisms, as well as their associated isotopic fractionations, are not well understood. We are investigating the use of Δ 17O as a quantitative and qualitative tracer for the different processes and oxygen sources involved in sulfate production. Δ17O signatures are distinct fingerprints of these reservoirs, independent of fractionation factors that can be ambiguous. We conducted controlled abiotic and biotic (Acidithiobacillus ferrooxidans, A.f.) laboratory experiments in which water was spiked with 18O, allowing us to quantify the sources of sulfate oxygen and therefore the processes attending sulfate formation. Results of this Δ17O tracer study show that A.f. microbes initiate pyrite S-oxidation within hours of exposure, and that sulfate is produced from ~90% atmospheric oxygen. This initial lag-phase (< 3 days) is characterized by subtle and multiple changes in oxygen source and contribution that is likely due to the adjustment of the microbial metabolism from S to Fe2+-oxidation. A more detailed understanding of the microbial mechanisms and behavior in the initial lag-phase will aid in the understanding of the ecological conditions required for microbial populations to establish and survive. An exponential phase of growth, facilitated by microbial Fe2+-oxidation, follows. The source of sulfate rapidly switches to abiotic sulfide oxidation during exponential growth and the source of oxygen switches from atmospheric O2 to nearly ~100% water. Pending acquisition of complimentary chemistry data (in progress), we interpret our isotope data to indicate that the biotic fractionation factor ɛ18OSO4-O2 of at least ~ -25 to - 35‰ is augmented by microbially induced kinetic fractionation; it is larger than expected based on published equilibrium values [2,3,4]. Our inferred ɛ18OSO4-H2O of at least ~+10‰ is similar to some reported values. These new insights into the close links between microbial life cycle and sources of sulfate oxygen during sulfide oxidation, and their oxygen isotopic expressions, will help elucidate the role of microbial oxidation in natural systems. If microbial populations in natural systems remain in a perpetual lag-phase due to constrains of chemistry, atmospheric oxygen will imprint its isotopic signature onto sulfate deposits. Ultimately, such data could be used as biosignatures on Early Earth or Mars. [1] Brunner and Coleman (2008) EPSL 270, 63-72. [2] Balci et al. (2007) GCA 71, 3796-3811. [3] Pisapia et al. (2007) GCA 71, 2474-2490. [4] Taylor et al. (1984) GCA 48, 2669-2678.
Coleman Max L.
Mielke Randall E.
Young Edward D.
Ziegler Karen
No associations
LandOfFree
Sources and Contributions of Oxygen During Microbial Pyrite Oxidation: the Triple Oxygen Isotopes of Sulfate does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Sources and Contributions of Oxygen During Microbial Pyrite Oxidation: the Triple Oxygen Isotopes of Sulfate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sources and Contributions of Oxygen During Microbial Pyrite Oxidation: the Triple Oxygen Isotopes of Sulfate will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1239481