Overlapping role of the outer membrane cytochromes of Shewanella oneidensis MR-1 in the reduction of manganese(IV) oxide.
OBJECTIVE
To determine if the outer membrane (OM) cytochromes OmcA and OmcB of the metal-reducing bacterium Shewanella oneidensis MR-1 have distinct or overlapping roles in the reduction of insoluble manganese(IV) oxide.


RESULTS
The gene replacement mutant (OMCA1) which lacks OmcA was partially deficient in Mn(IV) reduction. Complementation of OMCA1 with a vector (pVK21) that contains omcB but not omcA restored Mn(IV) reduction to levels that were even greater than those of wild-type. Examination of the OM of OMCA1/pVK21 revealed greater than wild-type levels of OmcB protein and specific haem content.


CONCLUSIONS
Overexpression of OmcB can compensate for the absence of OmcA in the reduction of insoluble Mn(IV) oxides. Therefore, there is at least a partial overlap in the roles of these OM cytochromes in the reduction of insoluble Mn(IV) oxide.


CONCLUSIONS
The overlapping roles of these two cytochromes has important implications for understanding the mechanism by which MR-1 reduces insoluble metal oxides. There is no obligatory sequential electron transfer from one cytochrome to the other. They could both potentially serve as terminal reductases for extracellular electron acceptors.
Myers
J M
JM
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Myers
C R
CR
D000693:Anaerobiosis; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D001426:Bacterial Proteins; D015153:Blotting, Western; D003574:Cytochrome c Group / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D003580:Cytochromes / Q000378:metabolism*; D017353:Gene Deletion; D017895:Manganese Compounds / Q000032:analysis / Q000378:metabolism*; D009154:Mutation; D010084:Oxidation-Reduction; D010087:Oxides / Q000032:analysis / Q000378:metabolism*; D020592:Shewanella / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003574:Cytochrome c Group; D003580:Cytochromes; D017895:Manganese Compounds; C436968:OmcB protein, bacteria; D010087:Oxides; C114590:omc A protein, Shewanella putrefaciens; C027424:manganese oxide