Predominance of Dehalococcoides in the presence of different sulfate concentrations

This is the first study that investigates in detail the effect of different sulfate concentrations on trichloroethene-dechlorinating microbial communities, both in terms of dechlorinating performance andmicrobial composition. The study used a series of Dehalococcoidescontaining trichloroethene-dechlorinating microbial communities, which operated for more than 800 days in the presence of different sulfate concentrations and limitingelectron donor conditions. This study proves the ability of Dehalococcoides spp., the only genus able to completely dechlorinate trichloroethene, to predominate in mixed anaerobic microbial communities regardless of the magnitude of sulfate concentration, even under limitingelectron donor conditions. Although other microorganisms, such as the Sulfurospirillum spp. bacteria and members of the sulfate-reducing bacteria group were able to thrive, they were not able to predominate in such a competitive environment. However, this picture was not reflected in reductive dechlorination, which demonstrated a much better performance under methanogenic conditions or in the presence of low sulfate concentration (30 mg/l) than in the presence of higher sulfate concentrations (>400 mg/l). Therefore, different species of Dehalococcoides or other dechlorinating bacteria, which are not able to thrive in the presence of high sulfate concentrations (>400 mg/l), are possibly responsible for the higher dechlorination efficiency that was observed under methanogenic conditions. © Springer Science+Business Media Dordrecht 2013.