Fluorescent pseudomonads associated with the phyllosphere of grasses; Pseudomonas trivialis sp. nov., Pseudomonas poae sp. nov. and Pseudomonas congelans sp. nov.

Strains of fluorescent pseudomonads, isolated from the phyllosphere of grasses, were analysed by a polyphasic approach in order to clarify their interspecific position. Classification on the basis of ribotyping revealed six genotypes; four of these, which could be differentiated clearly from each other and from Pseudomonas species with validly published names on the basis of phenotypic features, were chosen for detailed phylogenetic analysis. DNA-DNA hybridization studies among representative strains of the four genotypes and closely related Pseudomonas species, determined by comparison of 16S rDNA sequences, showed that three of the studied ribotypes represented novel species. Two of them were related to mainly saprophytic fluorescent pseudomonads and could be easily distinguished by a negative arginine dihydrolase reaction. One ribotype, also characterized by a negative arginine dihydrolase reaction, was closely related to potentially plant-pathogenic fluorescent pseudomonads and differed in certain phenotypic features from its phylogenetic neighbours. As a consequence of the phenotypic and phylogenetic analyses, Pseudomonas trivialis sp. nov. (type strain: P 513/19(T)=DSM 14937(T)=LMG 21464(T)), Pseudomonas poae sp. nov. (type strain: P 527/13(T)=DSM 14936(T)=LMG 21465(T)) and Pseudomonas congelans sp. nov. (type strain: P 538/23(T)=DSM 14939(T)=LMG 21466(T)) are proposed.