Pseudomonas belongs to the rRNA organism of group I of the gamma proteobacteria. They are rod-shaped gram-negative aerobes with polar flagella. They can be isolated from soil, decaying plant materials, and the rhizopheric region of numerous plant species. Strains of these bacteria called P. marginalis or P. fluorescens can be attributed to soft rot diseases in vegetables. The very complex groups of Pseudomonas, fluorescent soft rot and oxidase positive, are opportunistic macergens. The nomenclature of bacteria of the Pseudomonas genus has changed considerably in recent decades. P. marginalis are pectinolytic strains of P. fluorescens that cause soft rot on a wide range of hosts. The taxonomic and phytopathogenic status of P. marginalis is not well known, however they are biochemically and phenotypically indistinguishable from the saprophytic strains of P. fluorescens biovars II, P. putida, and P. voloraphis (now includes P. aureofaciens). Due to their ability to degrade pectin and macerate the parenimatous tissues of the plant they are called P. marginalis. Recently, based on 16S rRNA analysis, Anzai et al. (2000) identified 57 strains of Pseudomonas sensu stricto with seven subclusters: P. syringae group, P. chronoraphis group, P. fluorescens group, P. putida group, P. stutzeri group, P. aeruginosa group and P. pertucinogena group. Furthermore, in the Pseudomonas genus itself, some species have been misclassified, for example P. aureofaciens and P. aurantiaca, which were reclassified to P. muroraphis (Peix et al. 2007). Since the invention of the genus Pseudomonas it has undergone numerous taxonomic changes not only with regard to the number of species included but also with regard to the criteria used for their definition and delineation. In Berg...... half of the paper ......ies (Guasp et al. 2000). The selection of the minimum principles necessary for species delineation and description is selected for each bacterial genus by a committee created by experts in the genus in question. The methods used in the taxonomy of the genus Pseudomonas and related genera have been standardized by the Subcommittee on Taxonomy. However, minimum standards for the description of species of the genus Pseudomonas have yet to be clarified since the 2002 meeting of this subcommittee (De Vos and Yabuuchi 2002). Therefore, the description of the new species of this genus must be based on the general minimum standards for the characterization of bacterial species (Stackebrandt et al. 2002). These general minimum standards necessary for the classification of new species and/or subspecies must include 16S rRNA sequencing, DNA-DNA hybridization, fatty acid analysis and phenotypic classification.