Summary auto-generated
This study determined the phylogenetic position of Riemerella anatipestifer, a gram-negative bacterium that causes septicemia anserum exsudativa (new duckling disease) in domesticated ducks and turkeys. Researchers sequenced the 16s rRNA genes of four R. anatipestifer strains using PCR amplification and direct sequencing, then compared these sequences with related bacteria. The analysis confirmed that R. anatipestifer belongs to the family Flavobacteriaceae within rRNA superfamily V. Phylogenetic analysis revealed that Bergeyella zoohelcum is the most closely related species (92.8% sequence homology), followed by several Chryseobacterium species (91.4-92.6% homology). The four R. anatipestifer strains showed 0.5-1.0% sequence variation among their 16s rRNA genes but occupied the same phylogenetic position. Restriction fragment length polymorphism analysis detected minor heterogeneity even within serotypes, confirming that intraspecific variation exists in R. anatipestifer populations. These findings support classifying R. anatipestifer as a separate genus within the Flavobacteriaceae family and demonstrate that genetic variation occurs between strains regardless of serotype.
Key findings
- 16s rRNA gene sequencing confirmed R. anatipestifer belongs to the family Flavobacteriaceae in rRNA superfamily V
- Bergeyella zoohelcum is the most closely related species at 92.8% sequence homology, with Chryseobacterium species showing 91.4-92.6% homology
- The four R. anatipestifer strains examined showed 0.5-1.0% variation in 16s rRNA sequences but occupied identical phylogenetic positions
- RFLP analysis detected genetic variation within individual serotypes, indicating intraspecific heterogeneity independent of serotype classification
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Abstract
Riemerella anatipestifer, the causative agent of septicemia anserum exsudativa (also called new duckling disease), belongs to the family Flavobacteriaceae of gram-negative bacteria. We determined the DNA sequences of the rrs genes encoding the 16S rRNAs of four R. anatipestifer strains by directly sequencing PCR-amplified rrs genes. A sequence similarity analysis confirmed the phylogenetic position of R. anatipestifer in the family Flavobacteriaceae in rRNA superfamily V and allowed fine mapping of R. anatipestifer on a separate rRNA branch comprising the most closely related species, Bergeyella zoohelcum, as well as Chryseobacterium balustinum, Chryseobacterium indologenes, and Chryseobacterium gleum. The sequences of the rrs genes of the four R. anatipestifer strains varied between 0.5 and 1.0%, but all of the strains occupied the same position on the phylogenetic tree. In general, differences in rrs genes were observed among R. anatipestifer strains, even within a given serotype, as shown by restriction fragment length polymorphism of PCR-amplified rrs genes.