HR: 14:25h
AN: B42C-04 INVITED     [PDF]
TI: Silicification of Thermophilic Biofilms: Do Aquificales Affect the Mineralisation Process?
AU: * Konhauser, K
EM: kurtk@ualberta.ca
AF: University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB T5N 2A2 Canada
AU: Lalonde, S
EM: stefanw@ualberta.ca
AF: University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB T5N 2A2 Canada
AU: Aguiar, P
EM: aguiar@pdx.edu
AF: Portland State University, Department of Biology, \ 1719 SW 10th Ave, Portland, Or 97201 United States
AU: Reysenbach, A
EM: reysenbacha@pdx.edu
AF: Portland State University, Department of Biology, \ 1719 SW 10th Ave, Portland, Or 97201 United States
AB: In geothermal environments, biomineralisation is an inevitable consequence of microbes growing in solute-rich waters. The process of silicification is of particular interest due to (1) apparent discrepancies between natural and laboratory silicification rates and (2) siliceous microfossils currently serve as the earliest physical evidence for life on Earth. Although mesophilic microbe-silica interactions have been studied in great detail, there is a paucity of information on the role that thermophiles play in the silicification process, i.e., does their metabolism in any way facilitate silicification and do their cellular remains fossilise? To help resolve some of these uncertainties, a thermophilic, biofilm-forming member of the Aquificales order, Sulfurihydrogenobium azorense, was grown in the presence of various concentrations of silica, ranging from undersaturated to those extremely supersaturated with respect to amorphous silica. Since the chemolithoautotrophic Aquificales use of a wide range and combination of electron donors and acceptors, the bacteria cultured were grown in the presence of H2 with O2, S and Fe(III) as terminal electron acceptors. This study focused on the rates of pH-induced silica polymerisation during a 48 hour interval, when the soluble silica phase was at its most reactive stage, and when the greatest amount of silica immobilisation was likely to occur. S. azorense was found to have no detectable effect on the polymerisation rate of silica under any condition tested, nor did it cause silica to precipitate in undersaturated conditions. In addition, transmission electron microscopy showed that although silica did indeed precipitate from solution, there was no obvious association between solid-phase silica and the cells walls. This suggests that under high silica levels there is such a strong chemical driving force for silica polymerisation, homogeneous nucleation, and ultimately silica precipitation that there is no obvious need for microbial catalysis.
DE: 1030 Geochemical cycles (0330)
DE: 1045 Low-temperature geochemistry
DE: 1055 Organic geochemistry
DE: 1065 Trace elements (3670)
DE: 4803 Bacteria
SC: Biogeosciences [B]
MN: 2003 Fall Meeting