Frequent concomitant presence of Desulfitobacterium spp. and “Dehalococcoides” spp. in chloroethene-dechlorinating microbial communities

The presence of chloroethene dechlorination activity as well as several bacterial genera containing mainly organohalide respiring members was investigated in 34 environmental samples from 18 different sites. Cultures inoculated with these environmental samples on tetrachloroethene and amended weekly with a seven organic electron donor mixture resulted in eleven enrichments with cis-DCE, ten with VC, and eleven with ethene as dechlorination end product, and only two where no dechlorination was observed. “Dehalococcoides” spp. and Desulfitobacterium spp. were detected in the majority of the environmental samples independently of the dechlorination end product formed. The concomitant presence of “Dehalococcoides” spp. and Desulfitobacterium spp. in the majority of the enrichments suggested that chloroethene dechlorination was probably the result of catalysis by at least two organohalide respiring genera either in parallel or by stepwise catalysis. A more detailed study of one enrichment on cis-DCE suggested that in this culture Desulfitobacterium spp. as well as “Dehalococcoides” spp. dechlorinated cis-DCE whereas dechlorination of VC was only catalyzed by the latter.