A Role for Dehalobacter spp. in the Reductive Dehalogenation of Dichlorobenzenes and Monochlorobenzene

Abstract

Previously, we demonstrated the reductive dehalogenation of dichlorobenzene (DCB) isomers to monochlorobenzene (MCB), and MCB to benzene in sediment microcosms derived from a chlorobenzene-contaminated site. In this study, enrichment cultures were established for each DCB isomer and each produced MCB and trace amounts of benzene as end products. MCB dehalogenation activity could only be transferred in sediment microcosms. The 1,2-DCB-dehalogenating culture was studied the most intensively. Whereas Dehalococcoides spp. were not detected in any of the microcosms or cultures, Dehalobacter spp. were detected in 16S rRNA gene clone libraries from 1,2-DCB enrichment cultures, and by PCR using Dehalobacter-specific primers in 1,3-DCB and 1,4-DCB enrichments and MCB-dehalogenating microcosms. Quantitative PCR showed Dehalobacter 16S rRNA gene copies increased up to 3 orders of magnitude upon dehalogenation of DCBs or MCB, and that nearly all of bacterial 16S rRNA genes in a 1,2-DCB-dehalogenating culture belonged to Dehalobacter spp. Dehalobacter 16S rRNA genes from DCB enrichment cultures and MCB-dehalogenating microcosms showed considerable diversity, implying that 16S rRNA sequences do not predict dehalogenation-spectra of Dehalobacter spp. These studies support a role for Dehalobacter spp. in the reductive dehalogenation of DCBs and MCB, and this genus should be considered for its potential impact on chlorobenzene fate at contaminated sites.

The restricted metabolism of the obligate organohalide respiring bacterium Dehalobacter restrictus: lessons from tiered functional genomics

“…[11][12][13][14], suggesting that the degradation potential of the genus Dehalobacter is largely beyond PCE and TCE. Finally, fermentation of dichloromethane by members of Dehalobacter has been shown [15,16], suggesting that not necessarily all members of this genus are obligate OHR bacteria (OHRB).…”

Dichloromethane Fermentation by a Dehalobacter sp. in an Enrichment Culture Derived from Pristine River Sediment

“…Dehalobacter spp. respire chlorinated ethenes (14), chlorinated ethanes (9, 27), 4,5,6,7-tetrachlorophthalide (31), ␤-hexachlorocyclohexane (28), and CF (8) and recently have been implicated in reductive dechlorination of dichlorobenzenes and monochlorobenzene (24).…”

Characterization of Microbes Capable of Using Vinyl Chloride and Ethene as Sole Carbon and Energy Sources by Anaerobic Oxidation

“…Sediment samples were obtained from a canal in Salem County, New Jersey entering the Delaware River from a site Zinder and colleagues have previously demonstrated reductive dehalogenation of chlorobenzenes (Fung et al, 2009;Nelson et al, 2011). Microcosms were inoculated using the sediment from a core sample 20-36 cm from water sediment interface obtained in May 2009 and stored at 4 o C in glass jars before use.…”

“…For the Balch tube experiments, organic acids such as lactate, succinate, and volatile fatty acids were determined by high performance liquid chromatography (HPLC) as previously described (Nelson et al, 2011) and had a detection limit of 10-20 µM. For the serum experiments, acetate was quantified using a Waters 600E High Performance Liquid Chromatograph (HPLC) system composed of an autosampler (Waters 717 plus), pumping system (Waters 600), and a UV/Vis detector (Model 490E) set at 210 nm.…”

“…Cycling condition were: 10 min at 95°C, 35 cycles of 15 s at 95°C and 1 min at 62°C, followed by melting curve analysis from 60 to 95°C to screen for primer dimers. Total bacterial 16S rRNA gene copy numbers were determined by analyzing a dilution series of a known quantity of a plasmid containing the appropriate part of the 16S rRNA gene from Bacillus subtilis strain 168 (Nelson et al, 2011). DNA concentrations were estimated spectrophotometrically using a ND-1000 spectrophotometer (Nanodrop, Wilmington, DE).…”