A D esulfitobacterium sp. strain PR reductively dechlorinates both 1,1,1‐trichloroethane and chloroform

Summary 1,1,1‐Trichloroethane ( TCA ) and chloroform are two notorious groundwater pollutants. Here we report the isolation and characterization of D esulfitobacterium sp. strain PR that rapidly dechlorinates both compounds. In pyruvate‐amended medium, strain PR reductively dechlorinates ∼ 1.0 mM TCA completely to monochloroethane within 15 days. Under the same conditions, strain PR dechlorinates ∼ 1.2 mM chloroform to predominantly dichloromethane (∼ 1.14 mM) and trace amount of monochloromethane (∼ 0.06 mM) within 10 days. Strain PR shares 96.7% 16 S rRNA gene sequence similarity with its closest relative – D esulfitobacterium metallireducens strain 853‐15; however, it distinguishes itself from known D esulfitobacterium strains by its inability of utilizing several of their commonly shared substrates such as lactate, thiosulfate and sulfite. A reductive dehalogenase gene ( ctrA ) in strain PR was identified to be responsible for dechlorination of both TCA and chloroform, showing a maximum expression level of 5.95 ∼ 6.25 copies of transcripts cell ‐1 . CtrA shares 94% amino acid sequence identity with CfrA in D ehalobacter sp. strain CF 50 and DcrA in D ehalobacter sp. strain DCA . Interestingly, strain PR could tolerate high aqueous concentrations (up to 0.45 mM) of trichloroethene, another groundwater pollutant that often coexists with TCA /chloroform. As the first chloroform‐respiring and the second TCA ‐respiring isolate that has been identified, D esulfitobacterium sp. strain PR may prove useful in remediation of halogenated alkanes with trihalomethyl (‐ CX 3 ) groups.