FIG. 6.

Neighbor-joining phylogenetic tree of nirS constructed using 32 cloned and partial amino acid sequences of 240 amino acids obtained from the three sites. They were compared with 33 sequences from GenBank and the sequence from our cultivated nirS denitrifying mangrove root isolate (purple). The clones were designated according to the site they were taken from: site 1, 1S (green); site 2, 2S (red); site 3, 3S (blue). We used the nirA sequence from Burkholderia cepacia (AB092344) as an outgroup. Bootstrap values greater than 500 from 1,000 replicate trees are reported at the nodes. The scale represents 10 mutations per 100 amino acid positions.