Assignment of Pseudomonas sp. strain E-3 to Pseudomonas psychrophila sp. nov., a new facultatively psychrophilic bacterium

Abstract.

A facultatively psychrophilic bacterium, previously described as Pseudomonas sp. strain E-3, has been reassigned by phenotypic characterization, chemotaxonomic analysis, DNA–DNA hybridization, and 16S rRNA gene phylogenetic analysis. The organism was a gram-negative, aerobic, straight rod with polar flagella. It was catalase positive and oxidase positive, able to grow at –1°C but not at 40°C, and produced acid from D-glucose under aerobic conditions. The major isoprenoid quinone was ubiquinone-9, and the DNA G+C content was 57.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that the bacterium is a member of the genus Pseudomonas and was closest to Pseudomonas fragi. Determination of the DNA–DNA relatedness between strain E-3 and P. fragi revealed too low a level of homology (47.9%–51.3%) to identify them as the same species. On the basis of phenotypic characteristics, phylogenetic analysis, and DNA–DNA relatedness data, it is concluded that strain E-3 represents an individual species. Accordingly, the name Pseudomonas psychrophila is proposed. The type strain is E-3^T (=JCM 10889).