Sulfur and Iron Cycling
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Microbially-Mediated Sulfur and Iron Cycling

George Luther(University of Delaware)
Jill Banfield (University of California at Berkeley)
David Emerson (George Mason University)
Eric Roden (University of Alabama)

     With Dr. Banfield's group we have studied the mechanism of polythionate oxidation at low pH which is facile with hydroxyl radicals formed on pyrite surfaces (Druschel et al, 2003). With Dr. Roden's group, we have investigated bacterial redox cycling at the oxic-anoxic interface with the neutrophilic Fe(II)-oxidizing bacterium strain TW2 and one paper is in press (Roden et al, 2004). With Dr. Emerson's group we have investigated the biotic oxidation rates of Fe(II) using the isolate ES-1 obtained from the Fe(II) seep at Contrary Creek, VA. The biotic oxidation rate is significant under microaerobic conditions and cannot be distinguished from the abiotic rate above 20 M O2. We have also discovered using our in situ solid-state voltammetric electrodes that FeSaq and FeMnSaq clusters are present in the environment (e.g., Fe(II) seeps) indicating that the sulfur cycle is intimately tied to the Fe cycle in fresh water environments. This and other Fe work were presented in Luther (2004) and Trouwborst et al (2004).      We are now designing a method with Dr. Emerson to use our electrodes to determine potential in situ Fe-oxidizing activities that can have broad applications in the field and in the lab. We plan further field research with the Biomars group and laboratory work exploring Fe cycling with microbial organisms with Drs. Emerson and Roden.

Recent Research:

  • Crosby, H. A., C. M. Johnson, E. E. Roden, and B. L. Beard. 2005b. Fe(II)-Fe(III) electron/atom exchange as a mechanism for Fe isotope fractionation during dissimilatory iron oxide reduction. Environ. Sci. Technol Submitted for publication.
  • Druschel, G., D. Emerson, B. Glazer, C. Kraiya, R. Sutka and G. W. Luther, III. 2004. Environmental limits of the circumneutral iron-oxidizing bacterial isolate ES-1: Field, culture, and kinetic results from voltammetric analyses. Geochimica Cosmochimica Acta Vol. 68 (11S), p. A387.
  • Johnson, C. M., E. E. Roden, S. A. Welch, and B. L. Beard. 2005. Experimental constraints on Fe isotope fractionation during magnetite and Fe carbonate formation coupled to dissimilatory hydrous ferric oxide reduction. Geochim. Cosmochim. Acta 69:963-993.
  • Johnson, C. M., B. L. Beard, E. E. Roden, D. K. Newman, and K. H. Nealson. 2004. Isotopic constraints on biogeochemical cycling of Fe. In C. M. Johnson, B. L. Beard, and F. Albarède (eds.). Geochemistry of Non-Traditional Stable Isotopes, Reviews in Mineralogy and Geochemistry 55, pp. 359-408. Mineralogical Society of America, Washington, DC.
  • Luther, III, G.W. and D. T. Rickard. 2005. Metal sulfide cluster complexes and their biogeochemical importance in the environment, Journal of Nanoparticle Research, in press.
  • Rentz, J.A., C. Kraiya, G.W. Luther, and D. Emerson. 2005. Measurement of environmental biological Fe2+-oxidizing activity. Astrobiology . 5:292.
  • Roden, E. E., D. Sobolev, B. Glazer, and G. W. Luther. 2004. Potential for microscale bacterial Fe redox cycling at the aerobic-anaerobic interface. Geomicrobiol. J. 21:379-391.
  • Sobolev, D., and E. E. Roden. 2002. Evidence for rapid microscale bacterial redox cycling of iron in circumneutral environments. Anton. van Leeuw. I81:587-597.
  • Trouwborst, R. E., G. M. Koch, G. W. Luther III and B. K. Pierson.  Iron Oxidation by Oxygenic Photosynthesis in the Precambrian: Support from contemporary hot spring microbial mats. Nature, in review.