Genetic Relationships among Eubacterium Species

Abstract

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. aluctolyticum, E. brachy, E. lenturn, 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 were shared among the 10 Eubacterium species. Therefore, the Eubacterium species we tested must be considered genetically distinct from each other.Numerous bacterial strains of non-spore-forming, grampositive, obligately anaerobic rods belonging to the genus Eubacterium have been isolated from human oral cavities (7), including those from dental plaque (3, 6, 16, 30), periodontal lesions (18,20,29,31), infected dental pulp (6,27), and carious dentine (1, 2, 5). Recognized among them in the past decade are many new species of Eubacterium (e.g., Eubacterium brachy, E. nodatum, E. timidum, E. yurii, and E. saphenum). Some of these species are associated with moderate and severe periodontitis and are less frequent in the supragingival sites or subgingival sites of healthy persons (13,19,32,34,35).The genus Eubacterium includes more than 40 species exhibiting diverse morphologies and shows biochemical, physiological, and serological heterogeneity (4,11,21,22,25,28,33). We have found that the oral Eubacterium species are clearly distinguished by serological reactions (24), and this immunological heterogeneity suggests that they are a genetically heterogeneous group of microorganisms. There is no comprehensive study of relationships among Eubacterium species by DNA reassociation, although the limited data on the G + C content of DNA suggests heterogeneity and the need for research.Ten species and two subspecies of the genus Eubacterium, including the type species and type strains, were selected for the present study. Variations in G + C content and DNA-DNA hybridization among these species were determined to assess the extent of heterogeneity among these Eubacterium species. 43714T, and E. yurii subsp. maGaretiae ATCC 43715T were used as representatives of these specie...

Phylogenetic and phenotypic evidence for the transfer of Eubacterium aerofaciens to the genus Collinsella as Collinsella aerofaciens gen. nov., comb. nov.

“…3 , 1986). Therefore, this genus contained many species with different characteristics and a broad range of G + C contents, which caused considerable confusion (Nakazawa & Hoshino, 1994).…”

“…E., Eubacterium; C., Collinsella. (Nakazawa & Hoshino, 1994 (Mountfort et al, 1988) can form the nucleus of a redefined genus Eubacterium. On the basis of the characteristics of this group, a preliminary working definition of Eubacterium sensu stricto should be as follows : Gram-positive rod-shaped organisms that are non-motile and obligately anaerobic, may form endspores and are saccharolytic.…”

Taxonomic characterization of Mogibacterium diversum sp. nov. and Mogibacterium neglectum sp. nov., isolated from human oral cavities.

“…DNA-DNA hybridization was performed using the membrane filter method as described previously (Meyer & Schleifer, 1978 ;Nakazawa & Hoshino, 1994). Briefly, reference DNA was labelled by using a multiprime DNA-labelling kit (Amersham) and [α-$#P]dCTP, and then purified with a Nick column (Pharmacia LKB Biotechnology).…”

“…DNA was isolated and purified using a modification of the Marmur protocol (Marmur, 1961 ;Nakazawa & Hoshino, 1994). The GjC content of the DNA was determined by HPLC, as described previously (Katayama-Fujimura et al, 1984).…”

“…Because of its broad definition, the genus has historically acted as a repository for a large number of diverse organisms (Cheeseman et al, 1996 ;, and it was inevitable that there was considerable heterogeneity among the species that were placed within it. It now contains many species and groups that are phylogenetically unrelated (Moore & Moore, 1986 ;Nakazawa & Hoshino, 1994). In recent studies, many oral AAGPR isolates have been described, some of which qualify as members of the genus Eubacterium but could not be assigned to any of the named species (Cheeseman et al, 1996 ;Poco et al, 1996a, b ;Wade et al, 1994 ;Sato et al, 1993a).…”