Biology
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p53d..04g&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #P53D-04
Biology
0404 Anoxic And Hypoxic Environments (4802, 4834), 0414 Biogeochemical Cycles, Processes, And Modeling (0412, 0793, 1615, 4805, 4912), 0419 Biomineralization, 0448 Geomicrobiology, 0463 Microbe/Mineral Interactions
Scientific paper
Many bacteria are capable of respiring on sulfate and other oxidized forms of sulfur under anaerobic conditions. The hydrogen sulfide that is formed during dissimilatory sulfate reduction (DSR) readily reacts with metals in the surrounding environment to form insoluble metal sulfides. Iron oxides are common substrata for colonization by sulfate-reducing bacteria (SRB) in sedimentary aquatic systems as well as in subsurface environments. While numerous studies have characterized iron sulfides formed during dissimilatory sulfate reduction by suspended populations of these bacteria in the presence of soluble iron, not much is known about those formed in the presence of biofilm populations associated with solid phase iron, particularly crystalline forms such as hematite. Under the latter conditions, we have observed the formation of the iron sulfide pyrrhotite, typically present in very low abundance in sediments and ore deposits compared to pyrite. The formation of pyrrhotite over pyrite is favored at low redox potential and sulfide activity, conditions we hypothesize are achieved at an iron oxide surface colonized by biofilm-forming SRB. Higher levels of hydrogenase activity by hematite surface-associated SRB than suspended cell populations likely promotes the low redox potential that favors pyrrhotite formation. The tendency for SRB in nature to associate with mineral particle surfaces, including iron oxides, suggests that some pyrrotite may have originated through biotic reactions. A comparison of the fine structure of pyrrhotite formed through these biotic processes with that formed under abiotic processes may reveal differences that provide a signature for biotically-derived pyrrhotite in the biosphere.
Geesey Gill G.
Neal A.
Reardon C.
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