ORIGINAL PAPER Influence of carbon sources and electron shuttles on ferric iron reduction by Cellulomonas sp. strain ES6 Robin Gerlach • Erin K. Field • Sridhar Viamajala • Brent M. Peyton • William A. Apel • Al B. Cunningham Received: 18 September 2010 / Accepted: 31 January 2011 / Published online: 13 February 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Microbially reduced iron minerals can reductively transform a variety of contaminants including heavy metals, radionuclides, chlorinated aliphatics, and nitroaromatics. A number of Cellulo- monas spp. strains, including strain ES6, isolated from aquifer samples obtained at the U.S. Department of Energy’s Hanford site in Washington, have been shown to be capable of reducing Cr(VI), TNT, natural organic matter, and soluble ferric iron [Fe(III)]. This research investigated the ability of Cellulomonas sp. strain ES6 to reduce solid phase and dissolved Fe(III) utilizing different carbon sources and various electron shuttling compounds. Results suggest that Fe(III) reduction by and growth of strain ES6 was dependent upon the type of electron donor, the form of iron present, and the presence of synthetic or natural organic matter, such as anthraquinone-2,6-disulfonate (AQDS) or humic substances. This research suggests that Cellulomonas sp. strain ES6 could play a significant role in metal reduction in the Hanford subsurface and that the choice of carbon source and organic matter addition can allow for independent control of growth and iron reduction activity. Keywords Fermenters Á Anthraquinone-2,6- disulfonate (AQDS) Á Humics Á HFO Á Ferrihydrite Á Goethite Á Magnetite Á Maghemite Á Hematite Introduction The reductive transformation of oxidized contami- nants by ferrous iron, Fe(II), has received increasing interest in the recent years. Electron transfer from Fe(II) usually occurs fast and is non-specific so that a broad spectrum of compounds can react with surface- associated and soluble Fe(II). This makes Fe(II)-based remediation technologies an attractive alternative or addition to traditional cleanup strategies. Potentially treatable contaminants include heavy metals such as R. Gerlach Á E. K. Field Á B. M. Peyton Á A. B. Cunningham Center for Biofilm Engineering, Montana State University, Bozeman, MT 59717, USA R. Gerlach (&) Á B. M. Peyton Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT 59717, USA e-mail: robin_g@biofilm.montana.edu E. K. Field Department of Microbiology, Montana State University, Bozeman, MT 59717, USA S. Viamajala Department of Chemical and Environmental Engineering, The University of Toledo, Toledo, OH 43606, USA W. A. Apel Biological Systems Department, Idaho National Laboratory, Idaho Falls, ID 83415, USA A. B. Cunningham Department of Civil Engineering, Montana State University, Bozeman, MT 59717, USA 123 Biodegradation (2011) 22:983–995 DOI 10.1007/s10532-011-9457-1