The use of 16S rDNA sequence analysis to investigate the phylogeny of Leptospiraceae and related spirochaetes.

The 16S rDNA sequences from 15 Leptospiraceae were determined by automated PCR-directed cycle sequencing. Nucleotide comparisons, including those from published sequences for Leptospira canicola Moulton and Serpulina spp., were used to construct phylogenetic trees. Serpulina hyodysenteriae and S. innocens were related to each other but were distinct from the Leptospiraceae comprising Leptospira parva incertae sedis (Turneria parva H), Leptonema illini and Leptospira spp. The pathogenic and the saprophytic leptospires were distinct and separated from each other. Leptospira inadai occupied an intermediate position between the two forms. The pathogens formed three groups. Group I was represented by L. interrogans sensu stricto and L. kirschneri, Group II by L. weilii, L. borgpetersenii and L. santarosai, and Group III comprised L. noguchii and L. meyeri. The saprophytic species, L. wolbachii and L. biflexa sensu stricto shared about 99% sequence similarity. The freshwater isolates were distinct from the marine isolate L. biflexa sensu lato ancona Ancona Porto.