Impact of magnetite nanoparticles on the syntrophic dechlorination of 1,2-dichlorIoethane

In anaerobic environments microorganisms exchange electrons with community members and with soil and groundwater compounds. Interspecies electron transfer (IET) occurs by several mechanisms: diffusion of redox compounds or direct contact between cells. This latter mechanism may be facilitated by the presence of conductive nanoparticles (NP), possibly serving as electron conduits among microorganisms. Our study examined the effect of magnetite (Fe3O4) NP on the dechlorination of 1,2-dichloroethane (1,2-DCA) by a mixed-culture. The addition of NP (170 mg L- 1 total Fe) enhanced the acetate-driven reductive dechlorination of 1,2-DCA to harmless ethene (via reductive dihaloelimination) up to 3.3-times (2.3 ?eq L- 1 d- 1 vs. 0.7 ?eq L- 1 d- 1), while decreasing the lag time by 0.8 times (23 days) when compared to unamended (magnetite-free) microcosms. Dechlorination activity was correlated with the abundance of Dehalococcoides mccartyi, which accounted up to 50% of total bacteria as quantified by CARD-FISH analysis, pointing to a key role of this microorganism in the process. Given the widespread abundance of conductive minerals in the environment, the results of this study may provide new insights into the fate of 1,2-DCA and suggest new tools for its remediation by linking biogeochemical mechanisms.