Pseudomonas putida is a major species belonging to the genus Pseudomonas. Although several hundred strains of P. putida have been deposited in culture collections, they potentially differ from the genetically defined "true Pseudomonas putida" because many were classified as P. putida based on their phenotypic and metabolic characteristics. A phylogenetic ana-lysis based on the concatenated sequences of the 16S rRNA and rpoD genes revealed that 46 strains of P. putida deposited in Japanese culture collections were classified into nine operational taxonomic units (OTUs) and eleven singletons. The OTU7 strain produces N-acylhomoserine lactone as a quorum-sensing signal. One of the OTU7 strains, JCM 20066, exhibited a ppuI-rsaL-ppuR quorum-sensing system that controls biofilm formation and motility. The P. putida type strain JCM 13063T and six other strains were classified as OTU4. Classification based on the calculation of whole-genome similarity revealed that three OTU4 strains, JCM 20005, 21368, and 13061, were regarded as the same species as JCM 13063T and defined as true P. putida. When orthologous genes in the whole-genome sequences of true P. putida strains were screened, PP4_28660 from P. putida NBRC 14164T (=JCM 13063T) was present in all true P. putida genome sequences. The internal region of PP4_28660 was successfully amplified from all true P. putida strains using the specific primers designed in this study.
Keywords: Pseudomonas putida; comparative genome; orthologue; quorum sensing; reclassification.