Phenotypically based taxonomy of psychrotrophic Pseudomonas isolated from spoiled meat, water, and soil

The phenetic taxonomy of 305 strains of Pseudomonas and related organisms was numerically studied by using 215 features, including 156 assimilation tests. A total of 200 field strains were isolated from spoiling meat, and 50 strains were isolated from freshwater or soil. In addition, 55 reference strains (including 23 type strains and 4 clinical strains) were obtained. The strains clustered into 25 clusters at the 75% level when the Jaccard similarity coefficient was used. The 10 clusters that were considered significant were assigned to the Pseudomonas fragi complex (131 strains), Pseudomonas lundensis (40 strains), Pseudomonas fluorescens biovar 1 (27 strains), P. fluorescens biovar 2 (5 strains), P. fluorescens biovar 3 (6 strains), P. fluorescens biovar 4 (16 strains), Pseudomonas aureofaciens-Pseudomonas chlororaphis (3 strains), Pseudomonas aeruginosa (4 strains), Pseudomonas glathei (2 strains), and Pseudomonas mephitica (2 strains). The P. fragi complex was further divided into subclusters; the major subcluster (comprising 93 strains, including the type strain) was regarded as P. fragi sensu stricto. P. fluorescens and allied bacteria closely matched the descriptions given by Stanier et al. (J. Gen. Microbiol. 43:159-271, 1966). The characteristics for the 10 significant clusters are given. Also given are criteria which differentiate the P. fragi subclusters. The phylogenetic relationships among the meat-associated taxa were calculated. P. fluorescens biovars 2 and 3 were clearly separated from the remaining taxa. Biovar 4 is the most conservative, while biovar 3 has evolved at the highest rate.