Characterization of tetrachloroethene dechlorinating cultures and isolation of a novel tetrachloroethene to cis-1,2-dichloroethene halorespiring bacterium

In this study anaerobic, microbial reductive dechlorination of tetrachloroethene (PCE) was investigated in enrichments that were obtained from contaminated soils using molecular biology methods. In addition, a novel PCE to cis-1,2-dichloroethene (cDCE) dechlorinating organism was isolated and characterized.; PCE to cDCE dechlorinating enrichment (TSS 3) at 10°C was characterized with amplification, cloning and sequencing of the 16S rDNA, and terminal-restriction fragment polymorphism (T-RFLP) analysis. The results suggested that TSS 3 contained at least two species: Pseudomonas sp. that persisted in an anaerobic culture through several transfers, and relative of a PCE dechlorinating bacterium, Dehalospirillum multivorans. Role of the Pseudomonas sp. was determined experimentally. The results showed that a Pseudomonas sp. isolate from TSS 3 was able to grow anaerobically with various substrates.; Psychrotrophic, PCE to cDCE dechlorinating Sulfurospirillum sp. strain JPD-1 was isolated anaerobically from TSS 3. JPD-1 grew at 2–30°C and dechlorinated PCE from 1.5 to 40°C; however, dechlorination was not sustained at 35°C and above. The temperature optima for growth and dechlorination were 25–30°C, where the generation time was 13 h and PCE dechlorination rate 5.6 ± 1.4 μmol PCE/mg protein·h. In addition to chloroethenes, JPD-1 used fumarate, NO₃−, NO₂ − and S0 as electron acceptors and was capable of microaerophilic and fermentative growth. Dechlorination was supported by H₂, pyruvate, formate and yeast extract. JPD-1 was a new species closely related to D. multivorans, Sulfurospirillum halorespirans and Sulfurospirillum sp. DSM 806.; Decay rates were estimated for JPD-1 at 10 and 26°C using initial biomass values, which were derived from PCE dechlorination curves using Monod equations for growth and substrate utilization. The decay rates ranged from 0.027 to 0.084 d−1 depending on temperature and yield coefficient.; Microbial communities in PCE or cDCE dechlorinating microcosms from contaminated soil were characterized with T-RFLP and PCR targeting three dechlorinating organisms. At least two PCE dechlorinating organisms were present in the microcosms. T-RFLP analysis showed that terminal fragment length (TRF) corresponding to Dehalococcoides sp. was observed in microcosms showing vinyl chloride and ethene production, while TRF corresponding to Desulfuromonas sp. BB1 was seen in a microcosm that transformed PCE to cDCE.