Physiological Characterization of a Bacterial Consortium Reductively Dechlorinating 1,2,3- and 1,2,4-Trichlorobenzene

Abstract

A bacterial mixed culture reductively dechlorinating trichlorobenzenes was established in a defined, synthetic mineral medium without any complex additions and with pyruvate as the carbon and energy source. The culture was maintained over 39 consecutive transfers of small inocula into fresh media, enriching the dechlorinating activity. In situ probing with fluorescence-labeled rRNA-targeted oligonucleotide probes revealed that two major subpopulations within the microbial consortium were phylogenetically affiliated with a sublineage within the Desulfovibrionaceaeand the gamma subclass of Proteobacteria. The bacterial consortium grew by fermentation of pyruvate, forming acetate, propionate, CO2, formate, and hydrogen. Acetate and propionate supported neither the reduction of trichlorobenzenes nor the reduction of sulfate when sulfate was present. Hydrogen and formate were used for sulfate reduction to sulfide. Sulfate strongly inhibited the reductive dechlorination of trichlorobenzenes. However, when sulfate was depleted in the medium due to sulfate reduction, dechlorination of trichlorobenzenes started. Similar results were obtained when sulfite was present in the cultures. Molybdate at a concentration of 1 mM strongly inhibited the dechlorination of trichlorobenzenes. Cultures supplied with molybdate plus sulfate did not reduce sulfate, but dechlorination of trichlorobenzenes occurred. Supplementation of electron-depleted cultures with various electron sources demonstrated that formate was used as a direct electron donor for reductive dechlorination, whereas hydrogen was not.

Behavior of sulfate reducing bacteria under oligotrophic conditions and oxygen stress in particle-free systems related to drinking water

“…Cells were concentrated by centrifugation (8000× g , 25 min, Sorvall RC‐5B centrifuge, Sorvall, Bad Homburg, Germany) and subsequently enriched in bicarbonate‐buffered, sulfide‐reduced mineral medium [21], supplemented with lactate (10 mM), ethanol (10 mM), benzoate (5 mM), acetate (20 mM) or propionate (10 mM), with sulfate (20 mM) as the electron acceptor. Medium preparation was performed according to Adrian et al [22]. After growth and production of sulfide, bacteria from enrichment cultures with lactate and ethanol were isolated by use of deep agar dilution series [21].…”

Estimation of microbial reductive transformation rates for chlorinated benzenes and phenols using a quantitative structure–activity relationship approach

“…Because of the strict screening criteria used in this study, the data set of rate constants was relatively small, consisting of rate constants from six separately published studies [3,[6][7][8][9][10][11][12][13]. The majority of the rate constants in the data set came from a single study [6][7][8] in which biotransformation rates were reported for a large number of chlorinated aromatic compounds in slurries containing sediment from an estuary in Japan.…”

“…2. Comparison of calculated versus observed rate constants (d Ϫ1 ) for the external validation data set [3,[9][10][11][12][13]. Calculated rate constants were evaluated using QSAR2.…”

Behavior of sulfate reducing bacteria under oligotrophic conditions and oxygen stress in particle-free systems related to drinking water

“…Cells were concentrated by centrifugation (8000Ug, 25 min, Sorvall RC-5B centrifuge, Sorvall, Bad Homburg, Germany) and subsequently enriched in bicarbonate-bu¡ered, sul¢de-reduced mineral medium [21], supplemented with lactate (10 mM), ethanol (10 mM), benzoate (5 mM), acetate (20 mM) or propionate (10 mM), with sulfate (20 mM) as the electron acceptor. Medium preparation was performed according to Adrian et al [22]. After growth and production of sul-¢de, bacteria from enrichment cultures with lactate and ethanol were isolated by use of deep agar dilution series [21].…”