FIG. 1.

Phylogenetic tree based on 16S rRNA gene sequences of Betaproteobacteria from the pilot plant. The relative abundances of the operational taxonomic units were based on the frequencies of the characteristic restriction patterns of the sequences belonging to one operational taxonomic unit divided by the total number of clones in the samples as shown in Table 2. 16S rRNA gene sequences of Acidiphilium angustum and Desulfurella acetivorans were used as outgroups. Lines A, B, and C indicate single clusters in the class Betaproteobacteria. Wi, water sample from the inflow area; Wo, water sample from the oxidation basin; Si, solid sample from the inflow area; So, solid sample from the oxidation basin. The relative abundances from the first and second DNA preparation steps (see the supplemental material) were not divided.