Fig. 2

Phylogenetic tree of partial NifH sequences. Alignment was made for the 192 amino acid residues corresponding to amino acid 34–184 in Azotobacter vinelandii NifH protein. The tree was constructed using the Neighbor-Joining method. The scale bar denotes 0.05 % of sequence distance. The retrieved sequences, in bold, were grouped into clusters A, B, C, D, E and F. The arrowhead sizes indicate the relative abundance of the genera. Bootstrap values above 50 % are indicated at the branching nodes. Jatropha isolates shown in light blue color indicate the presence of nifH gene as evidenced by PCR amplifications. The position of root isolates and leaf isolates is marked with red and green arrowheads, respectively