Abstract
In addition to its central role in mediating electron-transfer reactions within all living cells, iron undergoes extracellular redox transformations linked to microbial energy generation through utilization of Fe(II) as a source of chemical energy or Fe(III) as an electron acceptor for anaerobic respiration. These processes permit microbial populations and communities to engage in cyclic coupled iron oxidation and reduction within redox transition zones in subsurface environments. In the present paper, I review and synthesize a few case studies of iron-redox cycling in subsurface environments, highlighting key biochemical aspects of the extracellular iron-redox metabolisms involved. Of specific interest are the coupling of iron oxidation and reduction in field and experimental systems that model redox gradients and fluctuations in the subsurface, and novel pathways and organisms involved in the redox cycling of insoluble iron-bearing minerals. These findings set the stage for rapid expansion in our knowledge of the range of extracellular electron-transfer mechanisms utilized by subsurface micro-organisms. The observation that closely coupled oxidation and reduction of iron can take place under conditions common to the subsurface motivates this expansion in pursuit of molecular tools for studying iron-redox cycling communities in situ.
- iron
- metabolism
- microbe
- redox cycling
- subsurface environment
Footnotes
Electron Transfer at the Microbe–Mineral Interface: A Biochemical Society Focused Meeting held at University of East Anglia, Norwich, U.K., 2–4 April 2012. Organized and Edited by Jim Fredrickson (Pacific Northwest National Laboratory, U.S.A.), David Richardson (University of East Anglia, U.K.) and John Zachara (Pacific Northwest National Laboratory, U.S.A.).
Abbreviations: FeOB, Fe(II)-oxidizing bacteria; FeRB, Fe(III)-reducing bacteria; OM, outer membrane
- © 2012 The Authors Journal