The taxonomy of Pseudomonas fluorescens and Pseudomonas putida: current status and need for revision

Overview & Synopsis

Many studies are devoted to the ecology of Pseudomonas fluorescens and Pseudomonas putida. Indeed, bacteria belonging to these species could potentially be used for environmental purposes. Some strains are able to improve plant growth and plant health, and consequently could contribute to reduce the use of chemical inputs in agriculture. Others are able to dissimilate nitrates and to degrade xenobiotic compounds. Accurate identification of the bacterial strains tested in these ecological studies is needed. The purpose of this review is to describe the status of the taxonomy of P. fluorescens and P. putida and to present the methods available for speciation. The first works on the taxonomy of P. fluorescens and P. putida were based on phenotypic characters such as metabolic tests, fatty acid composition and protein profiles. These studies led to the subdivision of P. fluorescens and P. putida into 5 and 2 biovars, respectively. From these phenotypic characters, two dichotomous keys were proposed to differentiate quickly strains belonging to P. fluorescens and P. putida. The subdivision of these species into biovars indicates that identification based on phenotypic characters is not fully satisfactory. Further work has focused on genotypic characters based on the variability of consensus genes (rDNA) or of the total genome (DNA-DNA hybridization). Collectively, results from taxonomic studies of P. fluorescens and P. putida show that the present delineation of these two species is obsolete and that they should be divided in many nomenspecies. Further research, combining both recent phenotypic and genotypic methods, is required to clarify the taxonomy of P. fluorescens and P. putida.