Metal Reduction and Protein Secretion Genes Required for Iodate Reduction by Shewanella oneidensis

Abstract

Microbial iodate (IO 3 − ) reduction is a major component in the biogeochemical cycling of iodine and the bioremediation of iodine-contaminated environments; however, the molecular mechanism of microbial IO 3 − reduction is poorly understood. Results of the present study indicate that outer membrane (type II) protein secretion and metal reduction genes encoding the outer membrane MtrAB module of the extracellular electron conduit MtrCAB are required for IO 3 − reduction by S. oneidensis . On the other hand, the metal-reducing c -type cytochrome MtrC of the extracellular electron conduit is not required for IO 3 − reduction by S. oneidensis . These findings indicate that the IO 3 − electron transport pathway terminates with an as yet unidentified IO 3 − reductase that associates with the outer membrane MtrAB module to deliver electrons extracellularly to IO 3 − .