Isolation and characterization of Cr(VI) reducing Cellulomonas spp. from subsurface soils: Implications for long-term chromate reduction

Isolation and characterization of Cr(VI) reducing Cellulomonas spp. from subsurface soils: Implications for long-term chromate reduction

Sridhar Viamajala^a, William A. Smith^b, Rajesh K. Sani^c, William A. Apel^b, James N. Petersen^c, Andrew L. Neal^d, F.F. Roberto^b, D.T. Newby^b and Brent M. Peyton^c,*

^a National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Blvd., MS 3511, Golden, CO 80401, United States
^b Biological Sciences Department, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2203, United States
^c Center for Multiphase Environmental Research and Department of Chemical Engineering, Washington State University, P.O. Box 642710, Pullman, WA 99164-2710, United States
^d Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, SC 29802, United States

Abstract
Microbial enrichments from Cr(VI) contaminated and uncontaminated US Department of Energy Hanford Site sediments produced Cr(VI) reducing consortia when grown in the presence of Cr(VI) with acetate, D-xylose or glycerol as a carbon and energy source. Eight of the nine isolates from the consortia were Gram positive and four of these were identified by 16S rRNA sequence homology and membrane fatty acid composition as belonging to the genus Cellulomonas. Two strains, ES6 and WS01, were further examined for their ability to reduce Cr(VI) under growth and non-growth conditions. During fermentative growth on D-xylose, ES6 and WS01 decreased aqueous Cr(VI) concentrations from 0.04 mM Cr(VI) to below the detection limit (0.002 mM Cr(VI)) in less than three days and retained their ability to reduce Cr(VI) even after four months of incubation. Washed ES6 and WS01 cells also reduced Cr(VI) under non-growth conditions for over four months, both with and without the presence of an exogenous electron donor. K-edge XANES spectroscopy confirmed the reduction of Cr(VI) to Cr(III). The ability to reduce Cr(VI) after growth had stopped and in the absence of an external electron donor, suggests that stimulation of these types of organisms may lead to effective long-term, in situ passive reactive barriers for Cr(VI) removal. Our results indicate that Cr(VI) reduction by indigenous Cellulomonas spp. may be a potential method of in situ bioremediation of Cr(VI) contaminated sediment and groundwater.

Keywords: Cr(VI) reducing bacteria; Bioremediation; Cr(VI) reduction; Cellulomonas

*Corresponding author. Present address: Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT 59717-3920, United States.
Tel.: +1 406 994 7419
Fax: +1 406 994 5308
Email address: bpeyton@coe.montana.edu (B.M. Peyton)

Viamajala, S., W.A. Smith, R. K. Sani, W. A. Apel, J. N. Petersen, A. L. Neal, F. F. Roberto, D. T. Newby and B. M. Peyton. 2007. Isolation and characterization of Cr(VI) reducing Cellulomonas spp. from subsurface soils: Implications for long-term chromate reduction. Bioresource Technology, 98(3): 612-622.