Figure 1.

Neighbour-joining tree, computed based on the alignment of 16S rRNA gene sequences, showing the phylogenetic relationship of arsenic-respiring isolates with known arsenic resistant and dissimilatory arsenate reducing bacteria. The analysis included the data from ∼1400 nucleotide positions. The tree is a consensus of 100 neighbor-joining trees. Percentage values on each branch represent the corresponding bootstrap probability values obtained in 100 replications and numbers are shown only for values of >50%. Sequences derived from arsenic-respiring isolates (OM1, OM2, OM4, and OM17) are indicated in large bold red type; sequences derived from other dissimilatory arsenate reducing bacteria are indicated in black bold type. The remaining sequences indicated in normal type derived from strains that are only resistant to arsenic.