title: Precipitation of low-temperature dolomite from an anaerobic microbial consortium: the role of methanogenic Archaea.
abstract: Here we report precipitation of dolomite at low temperature (30 degrees 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 (Omega(dol) = 19.40) and increase by two orders of magnitude (Omega(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.
authors: Department of Geology, University of Kansas, Lawrence, KS, USA.
authors: P A
authors: PA
authors: Kenward
authors: R H
authors: RH
authors: Goldstein
authors: L A
authors: LA
authors: González
authors: J A
authors: JA
authors: Roberts
mesh_terms: D000693:Anaerobiosis; D001105:Archaea / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D002119:Calcium Carbonate / Q000378:metabolism*; D003080:Cold Temperature; D016172:DNA Fingerprinting; D019641:DNA, Archaeal / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D007501:Iron / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism*; D008697:Methane / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008910:Minnesota; D009691:Nucleic Acid Denaturation; D010084:Oxidation-Reduction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012988:Soil Microbiology; D014961:X-Ray Diffraction
chemical_list: D019641:DNA, Archaeal; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D007501:Iron; D002119:Calcium Carbonate; D008274:Magnesium; D008697:Methane; C028042:calcium magnesium carbonate