FIG. 3.

Neighbor-joining analysis of partial nirS gene products (167 amino acids) cloned from DNA isolated from marsh soil samples (M followed by number) or from marine sediment samples (p and w followed by number; p from Puget Sound and w from Washington coast [8]). The tree shows the topology of branching. Accession numbers are in brackets. nirF (accession no. D50473) and nirN (accession no. D84475) from Pseudomonas aeruginosa were used as outgroups. 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.