Reductive Dechlorination of Polychlorinated Biphenyls: Interactions of Dechlorinating Microorganisms With Methanogens and Sulfate Reducers

Abstract

Abstract-The potential role of methanogens and sulfate reducers in polychlorinated biphenyl (PCB) dechlorination was investigated using the specific inhibitors 2-bromoethanesulfonate for methanogens and molybdate for sulfate reducers and the most probable number technique. Sediments were spiked with Aroclor 1248 (300 g/g). The inhibition of sulfate reducers did not have any effect on Aroclor 1248 dechlorination or on the size of dechlorinating populations, which indicates that they were not directly involved. On the other hand, the inhibition of methanogens reduced the rate and extent of dechlorination but did not affect the size of dechlorinating populations. These results indicate that there are at least two different dechlorinating populations-one of which requires the presence of methanogens for dechlorination and the other of which can dechlorinate independently. In the absence of methanogenesis, meta-substituted congeners, such as 25-2Ј5Ј-, 23-2Ј5Ј-, and 25-2Ј-chlorobiphenyls, were not dechlorinated. When both inhibitors were added, there was no dechlorination or growth of dechlorinating microorganisms, probably because of the growth inhibition by the high redox potential stemming from the absence of the two major respirators or because of the combined effects of inhibitors themselves.

Microbial Reductive Dechlorination of Weathered and Exogenous Co-planar Polychlorinated Biphenyls (PCBs) in an Anaerobic Sediment of Venice Lagoon

“…This hypothesis is also supported by the results of our recent work performed on another sediment of the same area of the Venice Lagoon (Fava et al 2003b). However, it cannot be totally excluded that methanogenic bacteria were involved in the process, as it has been reported for other marine sediments (Alder et al 1993), or that it was mediated by either sulfate-reducing and methanogenic bacteria along with fermentative bacteria, as it has been observed in other circumstances (Kim & Rhee 1999;Wiegel & Wu 2000).…”

Molecular characterization of polychlorinated biphenyl-dechlorinating populations in contaminated sediments

“…The predominant archaeal clone 1A and the exclusive archaeal groups 214A and 308A are nearly identical to Methanosarcina barkeri (98~99% identity). There is evidence that methanogens may play a role in certain meta dechlorinations (Chang et al, 1994;Kim and Rhee, 1999;Ye et al, 1999). A second methanogen group was identified in our RFLP analysis.…”

“…Our microcosm studies conducted with inocula from the St. Lawrence River sediment, which is primarily contaminated with Aroclor 1248, have demonstrated that there are at least two populations with different dechlorinating competence (Sokol et al, 1998;Kim and Rhee, 1999;Cho et al, 2000). When methanogens were inhibited with 2-bromoethanesulfonate (BES) in sediments amended with Aroclor 1248, the extent of dechlorination by St. Lawrence River sediment microorganisms was reduced by about half, indicating that some methanogens are involved in PCB dechlorination (Kim and Rhee, 1999). Using a combination of the dilution fractionation and most probable number (MPN) technique, we were able to distinguish populations of different competence and also quantify the population size (Cho et al, 2000).…”

Methanosarcina spp. Drive Vinyl Chloride Dechlorination via Interspecies Hydrogen Transfer

“…Previous studies indicate a positive influence of methanogens on anaerobic dechlorination of chloroethenes (7,20,43), polychlorinated biphenyls (30), and chloroform (55). However, the underlying processes are often poorly understood or are related to nondehalorespiratory mechanisms such as oxidative acetogenesis of VC (6,8) or beneficial influence of cofactors such as F430 and vitamin B 12 (55), which are involved in cometabolic reductive dechlorination (26).…”