Rathayibacter gen. nov., Including the Species Rathayibacter rathayi comb. nov., Rathayibacter tritici comb. nov., Rathayibacter iranicus comb. nov., and Six Strains from Annual Grasses

A new genus, Rathayibacter, is proposed to accommodate three species of gram-positive, aerobic, coryneform bacteria previously placed in the genus Clavibacter (Rathayibacter rathayi comb. nov., Rathayibacter tritici comb. nov., and Rathayibacter iranicus comb. nov.), as well as six strains that were isolated from annual cereal grasses, may be responsible for ryegrass toxicity, and are very similar to the recently described organism Clavibacter toxicus sp. nov. (I. T. Riley and K. M. Ophel, Int. J. Syst. Bacteriol. 42:64-68, 1992). The properties of members of the genus Rathayibacter include coryneform morphology, peptidoglycan based on 2,4-diaminobutyric acid (type B2γ), predominant menaquinones of the MK-10 type, and phosphatidylglycerol and diphosphatidylglycerol as basic polar lipids. The DNA base compositions range from 63 to 72 mol% G+C. The members of the new genus form a phenetic cluster distinct from Clavibacter spp. at a level of 71% (simple matching coefficient) and exhibit 7 to 9% DNA-DNA reassociation with strains of Clavibacter spp. In contrast to Clavibacter spp., most Rathayibacter strains are associated with nematodes belonging to the genus Anguina. The Rathayibacter species differ from species belonging to related genera (e.g., Clavibacter and Agromyces species) in the following characteristics: Menaquinone and whole-cell sugar compositions, results of lysozyme-sodium dodecyl sulfate test (which indicates differences in cell wall composition), ability to utilize a number carbon sources, resistance to bacteriocins of some Clavibacter spp., and other characteristics. The Rathayibacter species can be differentiated from each other by following characteristics: Presence or absence of xylose and galactose in the cell walls, fatty acid composition, ability to assimilate various sources of carbon and nitrogen, hydrolytic activity, tolerance to 5% NaCI and 0.03% potassium tellurite, susceptibility to iranicin, and absence or presence of plasmids of certain sizes. The type species of the genus Rathayibacter is R. rathayi. The type strains of the species are R. rathayi VKM Ac-1601 (= ICMP 2574), R. iranicus VKM Ac-1602 (= ICMP 3496), and R. tritici VKM Ac-1603 (= ICMP 2626).