A taxonomic study of bacteria isolated from grasses: a proposed new species Pseudomonas graminis sp. nov.

The taxonomic position of a yellow-pigmented group of bacteria, isolated fr om the phyllosphere of grasses was investigated. Results obtained from rest riction analysis of amplified 16S rDNA with seven endonucleases (Cfol, HaeI II, AluI, HinfI, MspI, Sau3A and ScrFI) showed identical restriction patter ns for each enzyme of all isolates studied, which suggests that all strains belong to the same species. The grass isolates displayed the characteristi cs of the genus Pseudomonas. They were Gram-negative, aerobic and rod-shape d 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 b eing given to the utilization of monosaccharides. The disaccharides tested were not utilized as substrates. The DNA base compositions of the tested st rains ranged from 60 to 61 mol% G+C. The major isoprenoid quinone of each w as ubiquinone Q-9 and hydroxy fatty acids were represented by 3-hydroxydode canoic acid and 2-hydroxydodecanoic acid. Comparison of 16S rDNA sequences showed that the bacteria were members of the genus Pseudomonas, with simila rity values between 91.5 and 97.7 %. DNA-DNA hybridization studies with clo sely related neighbours revealed a low level of homology (< 27 %), indicati ng that the isolates represent an individual species. On the basis of pheno typic and phylogenetic analyses a new species, Pseudomonas graminis sp. nov . (type strain DSM 11363(T)), is proposed.