FIG. 1.

Phylogenetic Fitch-Margoliash amoA dendrogram (PHYLIP, version 3.57c, global rearrangements and randomized input [three jumbles]), showing the relationship of cloned amoA sequences from an industrial WWTP (I-212) and a municipal WWTP (M-379 and M-20) with cultured ammonia oxidizers (37). The root was determined by using the gamma-subclass AOB sequence from Nitrosococcus oceani C-107 as an outgroup. The numbers in brackets are accession numbers for the amoA sequences. Clusters were labeled by using the assignments of Purkhold et al. (37).