Development and characterization of DehaloR^2, a novel anaerobic microbial consortium performing rapid dechlorination of TCE to ethene

Abstract

A novel anaerobic consortium, named DehaloR^2, that performs rapid and complete reductive dechlorination of trichloroethene (TCE) to ethene is described. DehaloR^2 was developed from estuarine sediment from the Back River of the Chesapeake Bay and has been stably maintained in the laboratory for over 2 years. Initial sediment microcosms showed incomplete reduction of TCE to DCE with a ratio of trans- to cis- isomers of 1.67. However, complete reduction to ethene was achieved within 10 days after transfer of the consortium to sediment-free media and was accompanied by a shift to cis-DCE as the prevailing intermediate metabolite. The microbial community shifted from dominance of the Proteobacterial phylum in the sediment to Firmicutes and Chloroflexi in DehaloR^2, containing the genera Acetobacterium, Clostridium, and the dechlorinators Dehalococcoides. Also present were Spirochaetes, possible acetogens, and Geobacter which encompass previously described dechlorinators. Rates of TCE to ethene reductive dechlorination reached 2.83 mM Cl- d(-1) in batch bottles with a Dehalococcoides sp. density of 1.54E+11 gene copies per liter, comparing favorably to other enrichment cultures described in the literature and identifying DehaloR^2 as a promising consortium for use in bioremediation of chlorinated ethene-impacted environments.

The roles of methanogens and acetogens in dechlorination of trichloroethene using different electron donors

“…and able to reduce TCE to ethene. We maintained the culture under anaerobic conditions as previously described (Duhamel et al 2004;Ziv-El et al 2011) and preconditioned the culture for TCE dechlorination by growing it for 1 month in a medium with 300 μM neat TCE in 160-mL serum bottles.…”

“…The capillary column used was an Agilent J&W scientific DB-624 (30 m long, 0.32 mm id, 0.5 μm thickness). Ethene and methane were measured by injecting 500 μL of headspace (with a gas-tight syringe) samples to the same GC ( Ziv-El et al 2011;Kranzioch et al 2013). N 2 was the carrier gas fed at a constant flow rate of 0.065 m 3 /day, and the temperature conditions for injector and detector were 180 and 220°C, respectively.…”

Efficient Metabolic Exchange and Electron Transfer within a Syntrophic Trichloroethene-Degrading Coculture of Dehalococcoides mccartyi 195 and Syntrophomonas wolfei

“…D. mccartyi exhibits specific restrictive metabolic requirements for a variety of exogenous compounds, such as hydrogen, acetate, corrinoids, biotin, and thiamine, which can be supplied by other microbial genera through a complex metabolic network (1,(5)(6)(7)(8). Therefore, the growth of D. mccartyi is more robust within functionally diverse microbial communities that are deterministically assembled than in pure cultures (5,8,9). Previous studies have shown that D. mccartyi uses hydrogen as its sole electron donor for TCE dechlorination and outcompetes other terminal electron-accepting processes such as methanogenesis and acetogenesis at low hydrogen partial pressures (10,11).…”

Effects of 1,1,1-trichloroethane on enzymatic activity and bacterial community in anaerobic microcosm form sequencing batch reactors

“…DhR-2/LM-G01 (HQ012837), which was isolated from estuarine sediments in the Back River of the Chesapeake Bay. It performs rapid and complete reductive dechlorination of trichloroethene (TCE) to ethane, and the reaction rates reached to 2.83 Mm/Cl day in batch bottles (Ziv-El et al 2011). Band 9 had high similarity (99%) to bacteria DCE25 (AJ249227), which had an average dechlorination rate of 7.6 mmol/(g VSS) day, with a maximum dechlorination rate of 28.3 mmol/(g VSS) day (Middeldorp et al 2010).…”

“…The initially dominant Proteobacteria and Bacteroidetes species (bands 1, 2, 4, 5 and 6) decreased or disappeared, while species belonging to the phyla Proteobacteria, Spirochaetes, Firmicutes, and Bacteroidetes became dominant species (bands 7, 8, 10, 12, 13, 14 and 15) when enriched by TCA exposure in toluene degrading condition. The newly enriched species, bands 7 and 10, belonged to phyla Clostridium and Bacterium with TCA-degrading capabilities (Dong et al 2011;Ziv-El et al 2011), which might be the functional populations in the ASBR system. Under methanogenic conditions, more bands and types of bacteria appeared than in the control.…”