Electron shuttles alter selenite reduction pathway and redistribute formed Se(0) nanoparticles

• Electron shuttles greatly promote selenite reduction by S. oneidensis MR-1.
• Electron shuttles changes the reduction from inside to outside cells.
• Electron shuttles induce extracellular formation of selenium nanoparticles.

The reduction of selenite and formation of selenium nanoparticles tuned by electron shuttles was investigated using Shewanella oneidensis MR-1. Results showed that anthraquinone-2,6-disulfonate (AQDS) and riboflavin profoundly accelerated the reduction of selenite ranging from 0.5 to 5.0 mM. Selenite of 2.5 mM was completely removed from the solution after 12-h reduction by S. oneidensis MR-1 with OD600 of 0.5. The acceleration heavily depended on extracellular cytochromes OmcA and MtrC and bypassed the fumarate reductase FccA in the periplasm. These results indicated that electron shuttles diverted the selenite reduction from inside to outside cells. Consistently, extracellular formation of Se(0) nanoparticles was observed in the presence of AQDS, which will benefit for the extraction and purification of these nanoparticles. This study indicates that electron shuttles are readily controllable parameter for selenite reduction and biosynthesis of Se(0) nanoparticles.

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