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Summary

Electrodes poised at potentials low enough to serve as an electron donor for microbial respiration, but high enough to avoid the production of hydrogen, have been proposed as an alternative to the use of soluble electron donors for stimulating the bioremediation of chlorinated contaminants and/or metals. However, this form of respiration using pure cultures of microorganisms has only been reported in Geobacter species. To further evaluate this bioremediation strategy studies were conducted with Anaeromyxobacter dehalogenans, which has previously been reported to reductively dechlorinate 2-chlorophenol to phenol with acetate as the electron donor. Anaeromyxobacter dehalogenans could oxidize acetate with electron transfer to a graphite electrode poised at a positive potential, demonstrating its ability to directly exchange electrons with electrodes. Anaeromyxobacter dehalogenans attached to electrodes poised at −300 mV versus standard hydrogen electrode reductively dechlorinated 2-chlorophenol to phenol. There was no dechlorination in the absence of A. dehalogenans and electrode-driven dechlorination stopped when the supply of electrons to the electrode was disrupted. The findings that microorganisms other than Geobacter species can accept electrons from electrodes for anaerobic respiration and that chlorinated aromatic compounds can be dechlorinated in this manner suggest that there may be substantial potential for treating a diversity of contaminants with microbe–electrode interactions.