Phylogenetic affiliation of Pseudomonas putida biovar A and B strains

In the genus Pseudomonas, two main lineages and 19 phylogenetic groups or subgroups have been defined based on DNA sequence studies of 16S rRNA, gyrB and rpoD genes. In the present study, 33 strains previously classified as Pseudomonas putida were phylogenetically affiliated with their closest relatives in the genus by multilocus sequence analysis. The results demonstrated that strains assigned to biovar A of the species were located in the P. putida group, though not all belonged to the species P. putida. Biovar B strains were scattered among 6 subgroups of the Pseudomonas fluorescens group and also within the P. putida group. These results were corroborated when the entire genomes of 5 strains assigned to P. putida were analyzed. The phylogenetic results show that isolates of biovars A and B are in distinct phylogenetic groups. Thus, these biotypes are not reliable taxonomic markers.