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Applied and Environmental Microbiology, May 2000, p. 2006-2011, Vol. 66, No. 5
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Reduction of Fe(III), Cr(VI), U(VI), and Tc(VII) by Deinococcus radiodurans R1

J. K. Fredrickson,1,* H. M. Kostandarithes,1 S. W. Li,1 A. E. Plymale,1 and M. J. Daly2

Pacific Northwest National Laboratory, Richland, Washington 99352,1 and Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-47992

Received 20 January 2000/Accepted 8 March 2000

Deinococcus radiodurans is an exceptionally radiation-resistant microorganism capable of surviving acute exposures to ionizing radiation doses of 15,000 Gy and previously described as having a strictly aerobic respiratory metabolism. Under strict anaerobic conditions, D. radiodurans R1 reduced Fe(III)-nitrilotriacetic acid coupled to the oxidation of lactate to CO2 and acetate but was unable to link this process to growth. D. radiodurans reduced the humic acid analog anthraquinone-2,6-disulfonate (AQDS) to its dihydroquinone form, AH2DS, which subsequently transferred electrons to the Fe(III) oxides hydrous ferric oxide and goethite via a previously described electron shuttle mechanism. D. radiodurans reduced the solid-phase Fe(III) oxides in the presence of either 0.1 mM AQDS or leonardite humic acids (2 mg ml-1) but not in their absence. D. radiodurans also reduced U(VI) and Tc(VII) in the presence of AQDS. In contrast, Cr(VI) was directly reduced in anaerobic cultures with lactate although the rate of reduction was higher in the presence of AQDS. The results are the first evidence that D. radiodurans can reduce Fe(III) coupled to the oxidation of lactate or other organic compounds. Also, D. radiodurans, in combination with humic acids or synthetic electron shuttle agents, can reduce U and Tc and thus has potential applications for remediation of metal- and radionuclide-contaminated sites where ionizing radiation or other DNA-damaging agents may restrict the activity of more sensitive organisms.

* Corresponding author. Mailing address: Pacific Northwest National Laboratory, MSIN P7-50, P.O. Box 999, Richland, WA 99352. Phone: (509) 376-7063. Fax: (509) 376-1321. E-mail: jim.fredrickson{at}pnl.gov.

Applied and Environmental Microbiology, May 2000, p. 2006-2011, Vol. 66, No. 5
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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