FIG. 2.

Neighbor-joining analysis of partial nirK gene products (171 amino acids) cloned from DNA isolated from upland (U) and marsh (M) soil samples or from marine sediment samples from the Washington coast (w) (see reference 8). The tree shows the topology of branching. Accession numbers in brackets. The sequence from Nitrosomonas europaea was obtained from the preliminary whole-genome sequence (http://www.jgi.doe.gov/tempweb/JGI_microbial/html/index.html). aniA from Neisseria gonorrhoeae (accession no. M97926) was used as outgroup. A single sequence was chosen to represent all sequences in clusters consisting of >98% identical sequences, and in each case, the origin and number of the other sequences in the cluster are indicated in parentheses following the sequence name. Values indicate the percentage of 100 replicate trees supporting the branching order; values below 50 are omitted.