Summary auto-generated
This study sequenced the 16S rRNA gene of Dialister pneumosintes (formerly Bacteroides pneumosintes) to determine its proper phylogenetic classification. The organism was originally described in 1921 from respiratory secretions of influenza patients and has undergone several taxonomic reclassifications. Using molecular phylogenetic analysis, the researchers determined that D. pneumosintes belongs to the Sporomusa subbranch within the Clostridium subphylum of gram-positive bacteria, not the family Bacteroidaceae as previously classified. Within this branch, D. pneumosintes showed closest affinity to Megasphaera elsdenii and Veillonella species, though sequence divergences (11.5% and 12.2-12.8% respectively) indicated these represent separate genera. The findings support the recent resurrection of the genus Dialister by Moore and Moore to accommodate this organism. The results necessitate excluding D. pneumosintes from the Bacteroidaceae family and reclassifying it within the gram-positive bacterial lineage despite its gram-negative characteristics.
Key findings
- 16S rRNA sequencing places Dialister pneumosintes in the Sporomusa subbranch of the Clostridium subphylum, not in family Bacteroidaceae
- D. pneumosintes shows closest phylogenetic relationship to Megasphaera elsdenii and Veillonella species within the Sporomusa branch
- The organism's phylogenetic position differs markedly from the B. fragilis group, supporting its classification in the resurrected genus Dialister
- Sequence similarity to Sporomusa subbranch members (81-88%) is substantially higher than to B. fragilis group (70-72%)
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Abstract
The nucleotide sequence of the 16S rRNA gene of the type strain of Dialister pneumosintes was determined. Phylogenetic analysis revealed that this species belongs to the Sporomusa branch of the Clostridium subphylum of the gram-positive bacteria and should therefore be excluded from the family Bacteroidaceae. Within this branch, which encompasses several other gram-negative taxa, such as Acidaminococcus, Pectinatus, Phascolarcobacterium, Quinella, Selenomonas, and Zymophilus, Dialister showed a specific, albeit distant, affinity with the genera Megasphaera and Veillonella.