Carbon Nanotubes Alter the Electron Flow Route and Enhance Nitrobenzene Reduction by Shewanella oneidensis MR-1

Dissimilatory metal-reducing bacteria play an important role in environmental bioremediation, and their extracellular electron transfer (EET) and pollutant reduction process can be affected by various redox-active substances. While it is generally thought that these substances usually only accelerate the EET rate, here we discover that the electron flow route within Shewanella oneidensis MR-1 cells can also be altered by the introduction of carbon nanotubes (CNTs). Addition of 0.5% (w/v) CNTs in the cell-immobilized alginate beads led to a shift of intracellular nitrobenzene (NB) reduction to extracellular reaction and a 74% improvement in NB reduction efficiency. This work provides the first evidence that the electron flow route of microorganisms can be altered by CNTs. It broadens our view about the possible environmental consequence of CNTs from a microbial extracellular respiration perspective and may lead to an improved understanding of microbial respiration and improve the practical application of bioremediation processes.