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Precipitation of low‐temperature dolomite from an anaerobic microbial consortium: the role of methanogenic Archaea
Author(s) -
KENWARD P. A.,
GOLDSTEIN R. H.,
GONZÁLEZ L. A.,
ROBERTS J. A.
Publication year - 2009
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/j.1472-4669.2009.00210.x
Subject(s) - dolomite , methanogenesis , archaea , microcosm , temperature gradient gel electrophoresis , chemistry , calcite , biology , environmental chemistry , bacteria , methane , microbiology and biotechnology , mineralogy , ecology , 16s ribosomal rna , paleontology
Here we report precipitation of dolomite at low temperature (30 °C) mediated by a mixed anaerobic microbial consortium composed of dissimilatory iron‐reducing bacteria (DIRB), fermenters, and methanogens. Initial solution geochemistry is controlled by DIRB, but after 90 days shifts to a system dominated by methanogens. In live experiments conditions are initially saturated with respect to dolomite (Ω dol = 19.40) and increase by two orders of magnitude (Ω dol = 2 330.77) only after the onset of methanogenesis, as judged by the increasing [CH 4 ] and the detection of methanogenic micro‐organisms. We identify ordered dolomite in live microcosms after 90 days via powder X‐ray diffraction, while sterile controls precipitate only calcite. Scanning electron microscopy and transmitted electron microscopy demonstrate that the precipitated dolomite is closely associated with cell walls and putative extra‐cellular polysaccharides. Headspace gas measurements and denaturing gradient gel electrophoresis confirm the presence of both autotrophic and acetoclastic methanogens and exclude the presence of DIRB and sulfate‐reducing bacteria after dolomite begins forming. Furthermore, the absence of dolomite in the controls and prior to methanogenesis confirm that methanogenic Archaea are necessary for the low‐temperature precipitation of dolomite under the experimental conditions tested.