Chloroform respiration to dichloromethane by a Dehalobacter population

Abstract

Chloroform (CF), or trichloromethane, is an ubiquitous environmental pollutant because of its widespread industrial use, historically poor disposal and recalcitrance to biodegradation. Chloroform is a potent inhibitor of metabolism and no known organism uses it as a growth substrate. We discovered that CF was rapidly and sustainably dechlorinated in the course of investigating anaerobic reductive dechlorination of 1,1,1-trichloroethane in a Dehalobacter-containing culture. Like 1,1,1-trichloroethane dechlorination in this culture, CF dechlorination was a growth-linked respiratory process, requiring H(2) as an electron donor and CF as an electron acceptor. Moreover, the same specific reductive dehalogenase likely catalyzed both reactions. This Dehalobacter population appears specialized for substrates with three halogen substituents on the same carbon atom, with widespread implications for bioremediation.

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

“…CF can be cometabolically transformed under sulfate-reducing and methanogenic conditions (11,30), and a recent report demonstrated growth of a Dehalobacter sp. linked to reductive dechlorination of CF to DCM and inorganic chloride as end products (8). This finding suggested that CF organohalide respiration provides an additional source of DCM in anoxic environments.…”

“…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).…”

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).…”

Chlorine Isotope Effects from Isotope Ratio Mass Spectrometry Suggest Intramolecular C-Cl Bond Competition in Trichloroethene (TCE) Reductive Dehalogenation

“…Much fundamental interest is directed at the underlying reaction chemistry of the C-Cl bond [2][3][4]. The widespread industrial application of chlorinated hydrocarbons as solvents, chemical intermediates and pesticides resulted in environmental contamination, with adverse effects on drinking water quality and ecosystem and human health [5][6][7]. A specific focus has therefore been on their reductive dehalogenation to non-halogenated hydrocarbons, where detoxification is achieved by reductive cleavage of the carbon-chlorine bonds.…”