Electrochemical analyses of the electron transfer rates of MtrC and OmcA to hematite
EMSL Project ID
25403
Abstract
Decaheme c-type cytochromes MtrC and OmcA of Shewanella oneidensis MR-1 are hypothesized as terminal reductases to the insoluble forms of iron and manganese oxides [Fe(III)/Mn(III/IV)] because they are localized to the outer membrane of bacterial cells. Previously in the works funded by EMSL Biogeochemistry Grand Challenge, we found that purified MtrC and OmcA reduced hematite (Fe2O3), a solid form of Fe(III), by using a spectroscopic method. The reduction rates measured by this method, however, might not be the true electron transfer (ET) rates from MtrC and OmcA to hematite if the binding of MtrC or OmcA to hematite was the rate-limiting step, as MtrC and OmcA were chemically reduced prior to their binding. To accurately measure the ET rates from MtrC and OmcA to hematite, we propose to use an electrochemical method called protein film voltammetry (PFV) to quantitatively measure the direct ET from MtrC and OmcA to hematite. In this method, the reductions of hematite by MtrC and OmcA are determined after hematite binds to MtrC and OmcA. Thus, the measured reaction rates should be the true ET rates from the cytochromes to the solid metal oxide. Accurate measurements of electron transfer properties of MtrC and OmcA to hematite will contribute significantly to our understanding of the molecular mechanisms employed by microbial cells for anaerobic respiration of minerals.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-07-01
End Date
2010-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Reardon CL, A Dohnalkova, P Nachimuthu, DW Kennedy, D Saffarini, BW Arey, L Shi, Z Wang, DA Moore, JS Mclean, DM Moyles, MJ Marshall, JM Zachara, JK Fredrickson, and AS Beliaev. 2010. "Role of Outer-Membrane Cytochromes MtrC and OmcA in the Biomineralization of Ferrihydrite by Shewanella oneidensis MR-1." Geobiology 8(1):56-68. doi:10.1111/j.1472-4669.2009.00226.x