Binding and direct electrochemistry of OmcA, an outer-membrane cytochrome from an iron reducing bacterium, with oxide electrodes: A candidate biofuel cell system

Purification and Characterization of the [NiFe]-Hydrogenase of Shewanella oneidensis MR-1

“…Phenotypic analyses of MR-1 mutants reveal that while multiheme c-type cytochromes, such as MtrC and OmcA, are directly involved in reduction of Fe(III) oxides, Tc(VII), U(VI), and Cr(VI), [NiFe]-hydrogenase ([NiFe]-H 2 ase) has also been implicated in Tc(VII) reduction (2,3,6,23,24,31). Biochemical characterization of purified proteins demonstrated that MtrC and/or OmcA could bind to the surface of crystalline Fe(III) oxide hematite (␣-Fe 2 O 3 ) and reduce hematite as well as Tc(VII), U(VI), Cr(VI), and chelated Fe(III), providing direct evidence that MtrC and OmcA can serve as terminal reductases for extracellular reduction of these oxidized metals and metal contaminants (2,10,13,17,19,25,35,36,40,42). MR-1 [NiFe]-H 2 ase is believed to be localized in the periplasm, where it has been implicated in both H 2 formation and oxidation in addition to Tc(VII) reduction (24,26).…”

Controlling electron transfer at the microbe–mineral interface

“…The OmcA protein may form a 2:1 complex with MtrCAB, resulting in a system with 40 hemes that is referred to as the "OmcA-MtrCAB" complex in the paper of Okamoto et al (1). Protein film voltammetry measurements have shown that S. oneidensis OmcA and MtrC can transfer electrons rapidly and directly to graphite and hematite electrodes (13)(14)(15)(16). Most recently, the MtrCAB complex was reconstituted in proteoliposomes and shown to move electrons rapidly from an intravesicular electron pool to extravesicular nanoparticle suspensions of goethite, hematite, and lepidocrocite (17).…”

Nanosized Iron Oxide Colloids Strongly Enhance Microbial Iron Reduction

“…As another option, formation of conductive pili serving as nanowires was described as a possible way of transferring electrons to the oxide surface (15,34). Nevertheless, direct attachment has been recognized as a major mode of accessing iron oxides as electron acceptors (12). Direct transfer between microbial outer membrane reductases and the ferric minerals, however, requires close contact of less than 14 Å between the terminal iron reductase on the cell surface and the iron oxide molecule at the mineral surface (19,25), limiting the rates of electron transfer between cell and mineral.…”