Regiospecific dechlorination of spiked tetra- and trichlorodibenzo-p-dioxins by anaerobic bacteria from PCDD/F-contaminated Spittelwasser sediments

Samples were taken from sediment of the River Spittelwasser (district Bitte rfeld, Germany), which is highly polluted with PCDD/Fs and other chloroorga nic compounds. The sediment cores were separated into 10-20 cm thick layers , spiked with 50 muM of 1,2,3,4-tetrachlorodibenzo-p-dioxin and incubated f or 8 months under anaerobic conditions in the presence of cosubstrates. Red uctive dechlorination of the tetrachlorinated congener and formation of tri - and di-chlorinated products were observed in all biologically active incu bations. Analysis of subcultures spiked with 1,2,3- and 1,2,4-trichlorodibe nzo-p-dioxin, respectively, revealed two different dechlorination pathways within the sediment cores. Pathway M was characterized by the simultaneous dechlorination of peri- and lateralchlorine atoms, whereas sequence SP was restricted to the dechlorination at positions flanked by chlorine atoms on both sides. (C) 2001 Elsevier Science Ltd. All rights reserved.