by this technique and the OEUs that contain them were identified
as putative sulfate-reducing groups (Fig. 5). These results imply
that the genomes of the organisms corresponding to these four
OTUs contain dsrB and that the genomes of the rest of the organisms
in these OEUs do not. In the first of the putative sulfate-reducing
OEUs, the most abundant OTUs and two other OTUs appeared to
have the genetic capacity to reduce sulfate. In the second OEU, only
one OTU (about one-third as abundant as the most abundant OTU
in the OEU) appeared to have this capacity. In the third OEU, no
OTUs appeared to be capable of reducing sulfate.