Hydrogenase- and outer membrane c-type cytochrome-facilitated reduction of technetium(VII) by Shewanella oneidensis MR-1
Article first published online: 20 SEP 2007
Volume 10, Issue 1, pages 125–136, January 2008
How to Cite
Marshall, M. J., Plymale, A. E., Kennedy, D. W., Shi, L., Wang, Z., Reed, S. B., Dohnalkova, A. C., Simonson, C. J., Liu, C., Saffarini, D. A., Romine, M. F., Zachara, J. M., Beliaev, A. S. and Fredrickson, J. K. (2008), Hydrogenase- and outer membrane c-type cytochrome-facilitated reduction of technetium(VII) by Shewanella oneidensis MR-1. Environmental Microbiology, 10: 125–136. doi: 10.1111/j.1462-2920.2007.01438.x
- Issue published online: 20 SEP 2007
- Article first published online: 20 SEP 2007
- Received 13 June, 2007; accepted 11 August, 2007.
Pertechnetate, 99Tc(VII)O4–, is a highly mobile radionuclide contaminant at US Department of Energy sites that can be enzymatically reduced by a range of anaerobic and facultatively anaerobic microorganisms, including Shewanella oneidensis MR-1, to poorly soluble Tc(IV)O2(s). In other microorganisms, Tc(VII)O4– reduction is generally considered to be catalysed by hydrogenase. Here, we provide evidence that although the NiFe hydrogenase of MR-1 was involved in the H2-driven reduction of Tc(VII)O4–[presumably through a direct coupling of H2 oxidation and Tc(VII) reduction], the deletion of both hydrogenase genes did not completely eliminate the ability of MR-1 to reduce Tc(VII). With lactate as the electron donor, mutants lacking the outer membrane c-type cytochromes MtrC and OmcA or the proteins required for the maturation of c-type cytochromes were defective in reducing Tc(VII) to nanoparticulate TcO2·nH2O(s) relative to MR-1 or a NiFe hydrogenase mutant. In addition, reduced MtrC and OmcA were oxidized by Tc(VII)O4–, confirming the capacity for direct electron transfer from these OMCs to TcO4–. c-Type cytochrome-catalysed Tc(VII) reduction could be a potentially important mechanism in environments where organic electron donor concentrations are sufficient to allow this reaction to dominate.