Characterization of Hydrogenase and Reductive Dehalogenase Activities of Dehalococcoides ethenogenes Strain 195

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Abstract
Dehalococcoides ethenogenes strain 195 reductively dechlorinates tetrachloroethene (PCE) and trichloroethene (TCE) to vinyl chloride and ethene using H 2 as an electron donor. PCE- and TCE-reductive dehalogenase (RD) activities were mainly membrane associated, whereas only about 20% of the hydrogenase activity was membrane associated. Experiments with methyl viologen (MV) were consistent with a periplasmic location for the RDs or a component feeding electrons to them. The protonophore uncoupler tetrachlorosalicylanilide did not inhibit reductive dechlorination in cells incubated with H 2 and PCE and partially restored activity in cells incubated with the ATPase inhibitor N , N ′-dicyclohexylcarbodiimide. Benzyl viologen or diquat ( E o ′ ≈ −360 mV) supported reductive dechlorination of PCE or TCE at rates comparable to MV (−450 mV) in cell extracts.