Summary auto-generated
Tyzzer's disease is a fatal infection in laboratory rodents and other mammals caused by an organism historically classified as "Bacillus piliformis." This study used 16S rRNA sequence analysis to determine the true phylogenetic position of Tyzzer's bacillus. Researchers extracted nucleic acids from the organism cultured in mammalian cells, amplified and sequenced the 16S rRNA gene using polymerase chain reaction and reverse transcriptase sequencing, then constructed phylogenetic trees using maximum-likelihood, parsimony, and distance-based analyses. The results demonstrated that Tyzzer's bacillus clusters with a specific group of anaerobic bacteria, primarily Clostridium species, particularly Clostridium coccoides, C. oroticum, C. clostridiiforme, and C. symbiosum. Based on these molecular findings, the authors propose reclassifying Tyzzer's bacillus as Clostridium piliforme, with its 16S rRNA sequence serving as the species definition. This reclassification is supported by phenotypic characteristics such as the organism's anaerobic nature, spore production, gram-variable staining, and intestinal pathogenesis, all consistent with Clostridium species rather than Bacillus. The reclassification has practical implications for disease treatment and diagnosis using molecular methods.
Key findings
- 16S rRNA sequence analysis definitively places Tyzzer's bacillus within the genus Clostridium, not Bacillus, warranting reclassification as Clostridium piliforme
- Tyzzer's bacillus shares highest 16S rRNA sequence similarity with C. coccoides, C. oroticum, C. clostridiiforme, and C. symbiosum, forming a distinct phylogenetic group supported by bootstrap analysis (99% confidence with maximum-likelihood)
- The molecular reclassification aligns with phenotypic characteristics including anaerobic nature, spore production, gram-variable staining, and status as an intestinal pathogen, all typical of Clostridium species
- Two signature oligonucleotides (GAAGTATYTCGGTATGTAAA and TCCACCTGGGGAGTA) identify this phylogenetic group and can be used for diagnostic purposes
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Abstract
The small-subunit rRNA (16S rRNA) sequence of Tyzzer's bacillus (also known as "Bacillus piliformis") was elucidated by using the polymerase chain reaction followed by reverse transcriptase sequencing. By using maximum-likelihood analysis, a phylogenetic tree was constructed from this and other 16S rRNA sequences available from the first release of the Ribosomal Database Project (G. J. Olsen, R. Overbeek, N. Larsen, T. L. Marsh, M. J. McCaughey, M. A. Maciukenas, W.-M. Kuan, T. J. Macke, Y. Xing, and C. R. Woese, Nucleic Acids Res. 20:2199-2200, 1992). Tyzzer's bacillus grouped with a specific set of anaerobic bacteria, most of which are Clostridium spp. The closest identified relatives are Clostridium coccoides, Clostridium oroticum, Clostridium clostridiiforme, Clostridium symbiosum, and Streptococcus hansenii. Clostridium amino-valericum and "Acetitomaculum ruminis" are also solidly allied with this ensemble. We propose that Tyzzer's bacillus be reclassified as Clostridium piliforme on the basis of its 16S rRNA sequence.