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Applied and Environmental Microbiology, November 2008, p. 6880-6886, Vol. 74, No. 22
0099-2240/08/$08.00+0     doi:10.1128/AEM.00840-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Mechanism and Consequences of Anaerobic Respiration of Cobalt by Shewanella oneidensis Strain MR-1 {triangledown}

Heidi H. Hau,1,3 Alan Gilbert,2,3 Dan Coursolle,1,3 and Jeffrey A. Gralnick1,3*

Departments of Microbiology,1 Chemical Engineering,2 BioTechnology Institute, University of Minnesota—Twin Cities, St. Paul, Minnesota 551083

Received 11 April 2008/ Accepted 23 September 2008

Bacteria from the genus Shewanella are the most diverse respiratory organisms studied to date and can utilize a variety of metals and metal(loid)s as terminal electron acceptors. These bacteria can potentially be used in bioremediation applications since the redox state of metals often influences both solubility and toxicity. Understanding molecular mechanisms by which metal transformations occur and the consequences of by-products that may be toxic to the organism and thus inhibitory to the overall process is significant to future applications for bioremediation. Here, we examine the ability of Shewanella oneidensis to catalyze the reduction of chelated cobalt. We describe an unexpected ramification of [Co(III)-EDTA]– reduction by S. oneidensis: the formation of a toxic by-product. We found that [Co(II)-EDTA]2–, the product of [Co(III)-EDTA]– respiration, inhibited the growth of S. oneidensis strain MR-1 and that this toxicity was partially abolished by the addition of MgSO4. We demonstrate that [Co(III)-EDTA]– reduction by S. oneidensis requires the Mtr extracellular respiratory pathway and associated pathways required to develop functional Mtr enzymes (the c-type cytochrome maturation pathway) and ensure proper localization (type II secretion). The Mtr pathway is known to be required for a variety of substrates, including some chelated and insoluble metals and organic compounds. Understanding the full substrate range for the Mtr pathway is crucial for developing S. oneidensis strains as a tool for bioremediation.

* Corresponding author. Mailing address: BioTechnology Institute, University of Minnesota, 140 Gortner Lab, 1479 Gortner Ave., St. Paul, MN 55108. Phone: (612) 626-6496. Fax: (612) 625-5780. E-mail: gralnick{at}umn.edu

{triangledown} Published ahead of print on 3 October 2008.

Applied and Environmental Microbiology, November 2008, p. 6880-6886, Vol. 74, No. 22
0099-2240/08/$08.00+0     doi:10.1128/AEM.00840-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Baron, D., LaBelle, E., Coursolle, D., Gralnick, J. A., Bond, D. R. (2009). Electrochemical Measurement of Electron Transfer Kinetics by Shewanella oneidensis MR-1. J. Biol. Chem. 284: 28865-28873 [Abstract] [Full Text]  


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