GENETIC-RELATIONSHIPS AMONG EUBACTERIUM SPECIES

The genetic relationships among Eubacterium species were assessed by using DNAs from American Type Culture Collection type strains of 10 species and two subspecies of the genus Eubacterium, i.e., Eubacterium aerofaciens, E. alactolyticum, E. brachy, E. lentum, E. limosum, E. nodatum, E. rectale, E. saburreum, E. timidum, E. yurii subsp. yurii, and E. yurii subsp. margaretiae. The DNA base compositions (determined by highperformance liquid chromatography) of these species varied widely, from 38 to 62 mol% G+C. Seven Eubacterium species showed significant differences (nearly 10%) in G+C content compared with E. limosum, the type species of the genus. DNA-DNA hybridization (by the membrane filter method) showed that two subspecies, E. yurii subsp. yurii and E. yurii subsp. margaretiae, and two strains of E. timidum exhibited high levels of DNA relatedness. However, the DNA reassociations among the 10 Eubacterium species studied were 1 to 16%. None of the species examined shared a high level of DNA reassociation with the type species of the genus Eubacterium. The protein profile patterns (determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) of whole bacterial cells from these Eubacterium species were distinct, and no major peptide bands mere shared among the 10 Eubacterium species. Therefore, the Eubacterium species we tested must be considered genetically distinct from each other.