P19-05 : Biokinetic analysis of 1,2-DCA dechlorination by Geobacter sp. AY harboring a plasmid pAY30 coding 1,2-DCA reductive dehalogenase
1Dept. Civil Eng. Sys. Manag., Nagoya Inst. Technol., 2Environ. Sci. Inst. Nagoya city, 3Electronics-Inspired Interdisciplinary Res. Inst., 4Toyohashi Tech, EcoTopia Sci. Inst., Nagoya Univ., 5Center for Fostering Young and Innovative Researchers, Nagoya Inst. Technol.
Geobacter sp. AY, a dehalorespiring bacteria that dechlorinates 1,2-dichloroethane (DCA) to ethane, has the following advantages to be applied in bioremediation compared to yet isolated 1,2-DCA dechlorinators; the activity for 1,2-DCA higher than 1,000 ppm, the culturbility using only acetate as sole electron and carbon source, and the constitutive dechlorination activity. The genome analysis revealed that AY has chromosome DNA of about 3.9Mbp and a plasmid pAY30 of about 30kbp including gene encoding 12DCA dehalogenase (dcaA). For forecasting the bioremediation progress, the stability of plasmid probably has to be considered. In this study, the half velocity of constant (Ks), the maximum dechlorination velocity (Vmax) were determined for the cultures of AY grown on acetate and either fumarate, 1,2-DCA or the combination. In addition, the gene copy numbers of rpoB and dcaA were determined by qPCR. As the result, AY grown on 1,2-DCA has 8.8μM of Ks and 20×10-10μmol·h-1·cell-1 of Vmax. The Vmax is 10 hold faster than that for the dechlorination of 1,2-cisDCE by Dehalococcoides spp. While, the velocity and the copy number of dcaA were quite lower in the AY maintained without 1,2-DCA. As the conclusion, AY constitutively expressed 1,2-DCA dehalogenase, but the plasmid was not stable. The plasmid stability must be taken into account for the forecasting 1,2-DCA dechlorination by AY.