Bacterium · Takes chlorinated ethanes to ethene
Desulfitobacterium dichloroeliminans
It strips both chlorines off 1,2-dichloroethane in one step, so the product is ethene and not vinyl chloride. It has been injected into a contaminated aquifer and tracked while the contaminant came down.
| Contaminant | What the research documents |
|---|---|
| Chlorinated solvents & VOCs | Dichloroelimination of 1,2-dichloroethane to ethene with no vinyl chloride intermediate; the DcaA reductive dehalogenase |
From published research on the species, not tests of an Elm Dirt product. Studies often work with one strain, and sequencing identifies species, so results on a site are measured on that site.
On this page (5 sections)
What it is
Desulfitobacterium dichloroeliminans is an anaerobic soil and groundwater bacterium that breathes chlorinated chemicals. Most degraders eat a contaminant for carbon. This one uses it the way we use oxygen, as the compound that accepts electrons at the end of its metabolism.
It is one of the microbial species identified in Elm Dirt’s Bloom Juice by independent lab analysis (Biome Makers).
What the research shows
Most organisms that work on chlorinated solvents pull chlorines off one at a time, which is how a solvent site stalls at vinyl chloride, a compound more dangerous than its parent. This organism takes a different route called dichloroelimination, in which both chlorines leave at once and 1,2-dichloroethane becomes ethene with no vinyl chloride formed along the way [1]. It was the first bacterium shown to gain energy from that reaction.
The activity is constitutive, so the organism doesn’t need pre-growing on 1,2-dichloroethane before it starts [1].
The enzyme’s catalytic subunit, DcaA, was sequenced from an enrichment culture and from the organism itself [2]. In a direct comparison, DcaA turned 1,2-dichloroethane into ethene and 1,1,2-trichloroethane into vinyl chloride [3], so the compound going in decides what comes out.
In an in-situ bioaugmentation test at an industrial site in Belgium, strain DCA1 was injected into contaminated groundwater, and quantitative PCR tracked it moving from the injection well toward a monitoring well while 1,2-dichloroethane concentrations fell [4].
How it works
Reductive dehalogenases are cobalt-containing iron-sulfur enzymes that pass electrons to a carbon-chlorine bond and break it. In dihaloelimination the enzyme breaks two of those bonds on neighboring carbons at once, and the carbons close into a double bond. Ethene comes out whole, without stopping at vinyl chloride.
Where it fits
Being anaerobic, it works where the oxygen is gone: saturated ground, deeper soil, the inside of dense aggregates. Our aerobic hydrocarbon and PAH organisms want the opposite, so a site plan should say which zone does which job. Its target is chlorinated ethanes, a common legacy at manufacturing plants, degreasing operations and derailment sites; see chlorinated solvents and VOCs. Expect months to a year or more, with breakdown products tracked by an independent lab.
Studies
- De Wildeman S, Linthout G, Van Langenhove H, Verstraete W (2004). Complete lab-scale detoxification of groundwater containing 1,2-dichloroethane. Applied Microbiology and Biotechnology 63(5):609–612. doi:10.1007/s00253-003-1363-y
- Marzorati M, de Ferra F, Van Raemdonck H, Borin S, et al. (2007). A novel reductive dehalogenase, identified in a contaminated groundwater enrichment culture and in Desulfitobacterium dichloroeliminans strain DCA1, is linked to dehalogenation of 1,2-dichloroethane. Applied and Environmental Microbiology 73(9):2990–2999. doi:10.1128/AEM.02748-06
- Kunze C, Diekert G, Schubert T (2017). Subtle changes in the active site architecture untangled overlapping substrate ranges and mechanistic differences of two reductive dehalogenases. The FEBS Journal 284(20):3520–3535. doi:10.1111/febs.14258
- Maes A, Van Raemdonck H, Smith K, Ossieur W, et al. (2006). Transport and activity of Desulfitobacterium dichloroeliminans strain DCA1 during bioaugmentation of 1,2-DCA-contaminated groundwater. Environmental Science & Technology 40(17):5544–5552. doi:10.1021/es060953i
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