FIG. 1.

Phylogenetic tree showing relationships of small-subunit rRNA gene sequences obtained from environmental samples to those of Francisella and related species. The tree was rooted using sequences of Escherichia coli, Thiothrix ramosa, Caedibacter taenospiralis, Piscirikettsia salmonis, and Thiomicrospira thyasirae (not shown). The percentage of 100 bootstrap resamplings that support each topological element in maximum-likelihood analysis is indicated, for values of >70%. Phylogenetic groups of sequences obtained in this study are labeled I to V. Within these groups, sequences representative of the types obtained from Houston soil clone libraries (in red) are labeled with the sample name (soil samples 005 to 045 and one water sample) and by distinct sequence types within each sample (a to d). Numbers in parentheses indicate the percentage of clones with identical sequences obtained from that sample. Sequences in blue text are reference sequences obtained in this study. Sequences in black were obtained from GenBank, with accession numbers shown in parentheses. The scale bar corresponds to 0.05 substitution per nucleotide position.