The Mg-isotope biosignature of Escherichia coli-mediated olivine dissolution

Details The Mg-isotope biosignature of Escherichia coli-mediated olivine dissolution The Mg-isotope biosignature of Escherichia coli-mediated olivine dissolution

Dec 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufmpp34a..03g&link_type=abstract

American Geophysical Union, Fall Meeting 2005, abstract #PP34A-03

Biology

0406 Astrobiology And Extraterrestrial Materials, 0424 Biosignatures And Proxies, 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912), 4912 Biogeochemical Cycles, Processes, And Modeling (0412, 0414, 0793, 1615, 4805), 4924 Geochemical Tracers

Scientific paper

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, (OD600nm=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 (OD600nm=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)

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