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2,6-Dibromobiphenyl Primes Extensive Dechlorination of Aroclor 1260 in Contaminated Sediment at 8−30 °C by Stimulating Growth of PCB-Dehalogenating Microorganisms

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journal contribution
posted on 14.01.1999, 00:00 by Qingzhong Wu, Donna L. Bedard, Juergen Wiegel
We applied the most probable number (MPN) method to test the hypothesis that 2,6-dibromobiphenyl (26-BB) primes polychlorinated biphenyl (PCB) dechlorination by stimulating the growth of microorganisms that dehalogenate 26-BB and PCBs. The experiments were conducted in anaerobic microcosms of Aroclor 1260-contaminated sediment from Woods Pond (Lenox, MA). We estimate that the number of microorganisms capable of dehalogenating 26-BB and PCBs increased approximately 1000-fold (from 3−4.9 × 105 to 2−5.8 × 108 cells/g of sediment [dry weight] or from 0.7−1.2 × 105 to 0.5−1.4 × 108 cells/mL of wet sediment) after priming for 48 days with 26-BB (1050 μmol/L of slurry) in the presence of 10 mM malate at 22 °C. All MPN samples that showed debromination of 26-BB also dehalogenated Aroclor 1260 even in the high dilutions. These results demonstrate for the first time that halogenated biphenyls prime PCB dechlorination by stimulating the growth of PCB-dechlorinating microorganisms. 26-BB primed exclusively meta-dechlorination of the PCBs (Process N), which effected extensive decreases (75−88%) in the hexa- through nonachlorobiphenyls in only 5−8 months at temperatures as low as 8 °C. The highest observed rates of primed dechlorination of Aroclor 1260 ranged from ∼250 to ∼1150 pmol of Cl mL-1 day-1 at 8 and 25 °C, respectively.