Addition of Shewanella oneidensis MR-1 to the Dehalococcoides-containing culture enhances the trichloroethene dechlorination.

Dehalococcoides is able to completely dehalogenate tetrachloroethene (PCE) and trichloroethene (TCE) to ethene (ETH). However, the dechlorination efficiency of Dehalococcoides is low and result in the accumulation of toxic intermediates. In this study, Shewanella oneidensis MR-1 (S. oneidensis MR-1) was added to the Dehalococcoides-containing culture and the complete TCE to ETH dechlorination was shortened from 24 days to 16 days. Dehalococcoides-targeted 16S rRNA gene and two model reductive dehalogenase (RDase) genes (tceA and vcrA), responsible for dechlorinating TCE to vinyl chloride (VC) and VC to ETH respectively, were characterized. Results showed that S. oneidensis MR-1 has no effect on the cell growth while the RDase genes expression was up-regulated and the RDase activity of Dehalococcoides was elevated. The mRNA abundance of vcrA increased approximately tenfold along with the increased concentration of vitamin B12 (cyanocobalamin). Interestingly, the addition of S. oneidensis MR-1 increased the concentration of vitamin B12 by affecting the microbial community structure. Therefore, the addition of S. oneidensis MR-1 might have a positive effect on regulating the activity of RDase of functional microorganisms and uptake of vitamin B12, and further provided a practical vision of chloroethene dechlorination by the Dehalococcoides-containing culture.