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 513/19T=DSM 14937T=LMG 21464T), Pseudomonas poae sp. nov. (type strain: P 527/13T=DSM 14936T=LMG 21465T) and Pseudomonas congelans sp. nov. (type strain: P 538/23T=DSM 14939T=LMG 21466T) are proposed.

The taxonomic position of a yellow-pigmented group of bacteria, isolated from the phyllosphere of grasses was investigated. Results obtained from restriction analysis of amplified 16S rDNA with seven endonucleases (Cfol, Haelll, Alul, Hinfl, Mspl, Sau3A and ScrFl) showed identical restriction patterns for each enzyme of all isolates studied, which suggests that all strains belong to the same species. The grass isolates displayed the characteristics of the genus Pseudomonas. They were Gram-negative, aerobic and rod-shaped with polar flagella. Isolates were catalase-positive and oxidase-negative, and unable to oxidize or ferment glucose with the production of acid. The isolates did not reduce nitrate to nitrite but were able to utilize a wide range of compounds individually as a sole carbon source, with preference being given to the utilization of monosaccharides. The disaccharides tested were not utilized as substrates. The DNA base compositions of the tested strains ranged from 60 to 61 mol% G+C. The major isoprenoid quinone of each was ubiquinone Q-9 and hydroxy fatty acids were represented by 3-hydroxydodecanoic acid and 2-hydroxydodecanoic acid. Comparison of 16S rDNA sequences showed that the bacteria were members of the genus Pseudomonas, with similarity values between 91·5 and 97·7%. DNA-DNA hybridization studies with closely related neighbours revealed a low level of homology (< 27%), indicating that the isolates represent an individual species. On the basis of phenotypic and phylogenetic analyses a new species, Pseudomonas graminis sp. nov. (type strain DSM 11363^T), is proposed.

A representative selection of coryneform bacteria, isolated from the phyllosphere of grasses and the litter layer after mulching the sward, was characterized by a polyphasic approach to clarify their taxonomic position in the family Microbacteriaceae, with particular reference to potentially plant-pathogenic bacteria. On the basis of 16S rDNA analysis, the isolates can be classified into six genotypes representing the genera Curtobacterium, Clavibacter, Subtercola and a subgroup, which was not affiliated to a known genus. One genotype, belonging to the genus Curtobacterium, had an identical 16S rDNA sequence to reference strains of the Curtobacterium flaccumfaciens pathovars. Another genotype, closely related to the potentially pathogenic Curtobacterium flaccumfaciens, could be distinguished from known species of the genus on the basis of phylogenetic and phenotypic characterization and is consequently proposed as a novel species, Curtobacterium herbarum sp. nov. (type strain P 420/07T DSM 14013T = LMG 19917T). Two genotypes assigned to Clavibacter showed a close relationship to Clavibacter michiganensis subsp. tessellarius, a pathogenic bacterium causing foliar lesions on wheat. A further genotype, which clustered clearly in the genus Subtercola by comparison of 16S rDNA sequences, showed a hitherto undescribed B-type of peptidoglycan containing the diagnostic diamino acids ornithine and 2,4-diaminobutyric acid, in the cell wall; this genotype is proposed as Subtercola pratensis sp. nov. (type strain P 229/10T = DSM 14246T = LMG 21000T). For one genotype, which formed a phylogenetically separate branch in the family of Microbacteriaceae showing chemotaxonomic similarities to the genus Rathayibacter, a novel genus, Plantibacter gen. nov., is proposed; the type species is Plantibacter flavus sp. nov. (type strain P 297/02T = DSM 14012T = LMG 19919T).

In the context of studying the effects of transgenic fructan-producing potatoes on the community structure of phyllosphere bacteria, a group of strains closely related to the species Leifsonia ginsengi was isolated. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the new isolates and L. ginsengi DSM 19088^T formed a lineage at the genus level and this finding was supported by chemotaxonomic characterization. The peptidoglycan type of the representative isolate, K134/01^T, and L. ginsengi DSM 19088^T was B2γ, with d- and l-diaminobutyric acid as the diagnostic diamino acid and glycine, alanine and threo-3-hydroxyglutamic acid. The almost-complete substitution of glutamic acid by threo-3-hydroxyglutamic acid supported the differentiation of the new strains from recognized species of the genus Leifsonia. Furthermore, the detection of substantial amounts of the fatty acid cyclohexyl-C_17 : 0 in the new isolates and L. ginsengi DSM 19088^T was a prominent chemotaxonomic feature for a clear demarcation of these strains from all genera of the family Microbacteriaceae that display the B2γ cell-wall type. Comparative phylogenetic and phenotypic analyses of the isolates and L. ginsengi DSM 19088^T revealed the separate species status of the isolates. On the basis of these results, it is proposed that L. ginsengi should be classified as the type species of a novel genus, Herbiconiux gen. nov., with the name Herbiconiux ginsengi gen. nov., comb. nov. (type strain wged11^T = CGMCC 4.3491^T = JCM 13908^T = DSM 19088^T = NBRC 104580^T). The phyllosphere isolates are assigned to a novel species, Herbiconiux solani sp. nov. (type strain K134/01^T = DSM 19813^T = LMG 24387^T = NBRC 106740^T).