HR: 16:30h
AN: PP34A-03    [Abstracts]
TI: The Mg-isotope biosignature of Escherichia coli-mediated olivine dissolution
AU: Garcia, B
EM: Bruno.Garcia@ens-lyon.fr
AF: Lab. Sciences de la Terre, UMR5570, ENS Lyon, 46 allee d Italie, Lyon, 69364 France
AU: Lemelle, L
EM: Laurence.Lemelle@ens-lyon.fr
AF: Lab. Sciences de la Terre, UMR5570, ENS Lyon, 46 allee d Italie, Lyon, 69364 France
AU: Rose-Koga, E F
EM: e.koga@opgc.univ-bpclermont.fr
AF: Lab. Sciences de la Terre, UMR5570, ENS Lyon, 46 allee d Italie, Lyon, 69364 France
AU: Rose-Koga, E F
EM: e.koga@opgc.univ-bpclermont.fr
AF: Lab. Magmas et Volcans, UMR 6524, 5 rue Kessler, Clermont-Ferrand, 63038 France
AU: Telouk, P
EM: Philippe.Telouk@ens-lyon.fr
AF: Lab. Sciences de la Terre, UMR5570, ENS Lyon, 46 allee d Italie, Lyon, 69364 France
AU: Gillet, P
EM: Directeur@ens-lyon.fr
AF: Lab. Sciences de la Terre, UMR5570, ENS Lyon, 46 allee d Italie, Lyon, 69364 France
AU: * Albarede, F
EM: Francis.Albarede@ens-lyon.fr
AF: Lab. Sciences de la Terre, UMR5570, ENS Lyon, 46 allee d Italie, Lyon, 69364 France
AB: We report experimental evidence that Mg isotopes may be used as a geochemical tracer of biological activity. In contrast to H, O, C, N, and S, Mg is immune to atmospheric effects and therefore paves the way for the identification of ancient and/or extraterrestrial biological traces. The present work shows experimentally that, in the presence of olivine, Escherichia coli causes an enrichment of their host solution in ²⁴Mg relative to heavier isotopes. At low cellular concentrations, (OD_600nm=0.1), the magnitude of the Mg isotopic shift between the biotic versus the abiotic filtered solutions is -0.52±0.20‰ and increases to -1.88±0.40‰ at higher concentrations (OD_600nm=1). The δ²⁶Mg range of carbonates (-5.30±0.16 to -1.10±0.04 ‰ in Young and Galy, 2004), rises the question of whether the negative shift of δ²⁶Mg in carbonates could be an indicator of their biogenic origin. The δ²⁶Mg values of the bacterial cells and of the related aqueous solutions can be distinctly lower than that of terrestrial and extraterrestrial silicates (-1.10±0.12 to +6.74±0.001‰ e.g. Young and Galy, 2004) and reveal the presence of bacteria in silicate rocks (Lemelle et al. 2004). One significant geological application of these results could be the study of putative oldest life traces preserved in silica cherts (Westall et al., 2005). References E. D. Young and A. Galy in Geochemistry of non-traditional stable isotopes, C. M. Johnson, B. L. Beard and F. Albarede, Eds. (Reviews in Mineralogy and Geochemistry, 2004) 55, pp.197-230 L. Lemelle, M. Salome, M. Fialin, A. Simionovici, P. Gillet, Spectrochim. Acta B : Atom. Spectros. 59, 1703 (2004) F. Westall, Science, 308, 5720, 366-367 (2005)
DE: 0406 Astrobiology and extraterrestrial materials
DE: 0424 Biosignatures and proxies
DE: 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005