BIOREDUCTION OF NONTRONITE BY SHEWANELLA ONEIDENSIS MR-1 AND ITS OUTER MEMBRANE CYTOCHROME PROTEINS OMCA AND MTRC

Clay minerals are ubiquitous in soil environment, where bacterial metal reduction is an important biogeochemical process. Iron is an important component in clay and the ferric iron in clay minerals can be reduced by Shewanella oneidensis MR-1. The understanding of electron transfer pathways during this process is important for understanding metal redox cycling in sediments and utilizing MR-1 in bioremediation in a better way. It is known that the outer membrane cytochrome proteins OmcA and MtrC from MR-1 can act as terminal reductases capable of electron transfer to iron containing minerals such as hematite. However, according to our research, OmcA and MtrC are not the only pathways for electron transfer, when a kind of iron-containing clay mineral-nontronite is bioreduced by Shewanella oneidensis MR-1.