Conexibacter woesei gen. nov., sp. nov., a novel representative of a deep evolutionary line of descent within the class Actinobacteria A novel Gram-positive bacterial strain was isolated from forest soil. According to its 16S rRNA sequence, this strain is a deep-rooting member of the class Actinobacteria. The 16S rRNA sequence is most closely related (~94 % identity) to clones of uncultured bacteria detected in different terrestrial environments, while showing only a remote relationship (~90 % identity or less) to sequences of cultured species. Cells of the first cultured representative of this phylogenetic cluster are small, short rods that are motile by peritrichous flagella, catalase-and oxidase-positive and grow under aerobic conditions. In liquid culture, flagella from different cells can aggregate to form networks, clearly visible under the light microscope. The peptidoglycan contains mesodiaminopimelic acid and is directly cross-linked (type A1c). Mycolic acids are not present. The polar lipids are phosphatidylinositol and an unidentified phospholipid. Menaquinone MK-7(H 4 ) was detected as the predominant isoprenoid quinone. Oleic, 14-methylpentadecanoic, hexadecanoic and v6c-heptadecenoic acids are the predominant components of the cellular fatty acid profile. The DNA G+C content is 71 mol%. The distinct phylogenetic position and the unusual combination of chemotaxonomic characteristics justify the proposal of a new genus and species, Conexibacter woesei gen. nov., sp. nov., with the type strain ID131577 T (=DSM 14684 T =JCM 11494 T ).
INTRODUCTIONThe class Actinobacteria comprises bacteria that share >80 % 16S rRNA sequence similarity and a characteristic set of 16S rRNA signature nucleotides (Stackebrandt et al., 1997). The vast majority of cultured members of this class belong to the subclass Actinobacteridae. Only a few strains have been isolated that form deeply branching lines of descent within this class and have given rise to the description of the subclasses Acidimicrobidae, Rubrobacteridae, Sphaerobacteridae and Coriobacteridae (Stackebrandt et al., 1997). Molecular analyses of environmental DNA from various locations have revealed the presence of several clones that are phylogenetically related to the deeply branching members of Actinobacteria (Stackebrandt et al., 1993;Rheims et al., 1996; Felske et al., 1997). In some instances, the phylogenetic depth of clusters represented by these clones corresponds to that of subclasses or orders . However, attempts to isolate the corresponding microorganisms have so far been unsuccessful .A Gram-positive bacterium with a DNA G+C content of 71 mol% was isolated from forest soil. According to its 16S rDNA sequence, this strain belongs to a phylogenetic cluster consisting of clones of hitherto-uncultured bacteria that appear to be distributed worldwide in different soils (Rheims et al., 1996;. This isolate offers the first opportunity to study the phenotypic characteristics of one of these organisms. Because of the remote 16S rDNA similarity (<84 %) to va...