FIG. 4.

Phylogenetic tree showing distances based on the 16S rRNA sequences obtained from 27 clones from samples from the reservoir, the storage tank, the headwater tank, the top, middle, and bottom sand column layers, and outflow water from the experimental SSF unit. Sequences of the 16S rRNA genes of Legionella strains used for comparison in this study were retrieved from the EMBL DNA database (52). The 16S rRNA sequences obtained in this work are partial sequences (430 bp), and therefore their positions are indicated by dashed lines. The dendrogram was generated by using the programs DNASIST (maximum likelihood) and NEIGHBOR (neighbor joining). Scale bar = 0.1% estimated sequence divergence. Resampling (bootstrap analysis) was applied to the data, and the values obtained (percentages) are indicated at the nodes.