FIG. 2.

Phylogram showing the relationship between the nifH gene of the UMB cluster and other diazotrophic members of the γ-proteobacteria. The percentages (>50%) of 1,000 bootstrap replicates supporting the topography of the tree are shown at the nodes. The nifH gene from the δ-proteobacterium Desulfovibrio gigas was used as an outgroup. The inset phylogram shows the relationship between the nifH gene of the UMB clade including four previously reported environmental clones. The tree is based on all 242 bp of the nifH DNA sequences recovered and the corresponding coding regions of the previously reported clones.