FIG. 1.

Maximum-likelihood phylogenetic tree constructed using partial 16S rRNA gene sequences of closely related speciated and nonspeciated strains belonging to the alpha- and gamma-Proteobacteria. The tree is rooted using Nitrococcus mobilis (L35510) as the outgroup. Nucleotide sequence database accession codes are shown in the brackets. The length of each branch is proportional to the estimated number of substitutions per position. Sequenced strains are highlighted in boxes; most-likely identities were assigned.