PHYSIOLOGICAL CHARACTERIZATION OF A BACTERIAL CONSORTIUM REDUCTIVELY DECHLORINATING 1,2,3-TRICHLOROBENZENE AND 1,2,4-TRICHLOROBENZENE

A bacterial mixed culture reductively dechlorinating trichlorobenzenes was established in a defined, synthetic mineral medium without any co mplex 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 prob ing with fluorescence-labeled rRNA-targeted oligonucleotide probes rev ealed that two major subpopulations within the microbial consortium we re phylogenetically affiliated with a sublineage within the Desulfovib rionaceae and the gamma subclass of Proteobacteria. The bacterial cons ortium grew by fermentation of pyruvate, forming acetate, propionate, CO2, formate, and hydrogen, Acetate and propionate supported neither t he reduction of trichlorobenzenes nor the reduction of sulfate when su lfate was present, Hydrogen and formate were used for sulfate reductio n to sulfide. Sulfate strongly inhibited the reductive dechlorination of trichlorobenzenes. However, when sulfate was depicted in the medium due to sulfate reduction, dechlorination of trichlorobenzenes started . Similar results were obtained when sulfite was present in the cultur es, Molybdate at a concentration of 1 mM strongly inhibited the dechlo rination of trichlorobenzenes. Cultures supplied with molybdate plus s ulfate 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 electr on donor for reductive dechlorination, whereas hydrogen was not.