Summary auto-generated
Researchers characterized four previously unknown bacterial strains isolated from human clinical specimens using biochemical, chemical, and molecular taxonomic methods. The isolates were gram-positive, non-motile, catalase-negative rods that produced acid from glucose and fermented sugars to lactic and succinic acids. Whole-cell protein analysis showed the four strains formed a distinct, homogeneous group. Comparative 16S rRNA gene sequencing revealed the bacteria belonged to the genus Actinomyces but represented a new species, distinct from all previously recognized Actinomyces species with sequence divergence values exceeding 6%. Although the unidentified bacterium formed a loose association with the Actinomyces bovis subgroup, phylogenetic analysis unequivocally established its status as a new species. The clinical sources included respiratory tract secretions and jaw tissue from patients aged 27 to 57 years. Based on both phenotypic and phylogenetic distinctiveness, the researchers proposed the name Actinomyces graevenitzii for this new species, with type strain CCUG 27294.
Key findings
- Four human clinical isolates of gram-positive, facultatively anaerobic rods formed a phenotypically homogeneous group distinct from all known Actinomyces species
- 16S rRNA gene sequencing revealed >6% sequence divergence from other Actinomyces species, establishing the isolates as a new species lineage
- The new bacterium produced lactic acid as the major end product of glucose fermentation and demonstrated strong N-acetyl-β-glucosaminidase activity
- Actinomyces graevenitzii was proposed as a new species with type strain CCUG 27294, isolated primarily from respiratory tract specimens and jaw tissue
- Phylogenetic analysis demonstrated loose association with the Actinomyces bovis subgroup but confirmed distinct species-level status
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Abstract
Four strains of a previously unknown, catalase-negative, facultatively anaerobic, gram-positive, rod-shaped organism originating from humans were characterized by biochemical, chemical, and molecular taxonomic methods. The four strains phenotypically closely resembled one another, and although they possessed characteristics consistent with membership in the genus Actinomyces, they differed from all previously recognized species of this genus. The results of comparative 16S rRNA gene sequencing studies demonstrated that the unknown human bacterium was phylogenetically a member of the genus Actinomyces. Within the genus Actinomyces, the unidentified bacterium formed a loose, but statistically significant, association with a subgroup which included Actinomyces bovis, the type species of the genus. 16S rRNA sequence divergence values of >6%, however, unequivocally demonstrated that the unidentified bacterium represents a new subline of the genus Actinomyces. A new species, Actinomyces graevenitzii, is proposed for the four new isolates. The type strain of A. graevenitzii is CCUG 27294.