Summary auto-generated
This study describes three new Actinobacillus species isolated from the porcine respiratory tract. Using DNA-DNA hybridization and 16S rRNA gene sequencing, researchers identified three genetically distinct V factor-dependent bacteria previously classified as the Minor group and taxa D, E, and F within the Pasteurellaceae family. DNA-DNA hybridization experiments showed these three taxa represented separate phylogenetic groups with low relatedness to known species. The three new species, designated Actinobacillus minor, Actinobacillus porcinus, and Actinobacillus indolicus, represent resident microflora of the porcine upper respiratory tract. Each species has distinct biochemical characteristics including differential fermentation patterns, urease reactions, and indole production. The species differ in DNA G+C content: A. minor (38.2 mol%), A. porcinus (41.4 mol%), and A. indolicus (35.5 mol%). Phylogenetic analysis positioned these new species within the Pasteurellaceae family, with A. minor and a Minor group strain in one phylogenetic group, while A. porcinus and A. indolicus clustered together with Haemophilus parasuis. This work demonstrates that V factor dependence is not exclusive to Haemophilus but distributed throughout the Pasteurellaceae family.
Key findings
- Three new Actinobacillus species (A. minor, A. porcinus, and A. indolicus) were identified from pig respiratory tracts based on DNA-DNA hybridization and 16S rRNA sequencing
- The three species showed low DNA relatedness to each other and to established Pasteurellaceae members, supporting their designation as distinct species
- DNA G+C content differed among the three species: A. minor 38.2%, A. porcinus 41.4%, and A. indolicus 35.5% mol%
- Biochemical characteristics differentiate the species, particularly urease and indole reactions and carbohydrate fermentation patterns
- V factor dependence was confirmed to be distributed throughout the Pasteurellaceae family, not limited to the genus Haemophilus
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Abstract
The results of DNA-DNA relatedness experiments and comparisons of sequences of genes coding for 16S rRNA were used to determine the genetic relationships of selected V factor-dependent species belonging to the family Pasteurellaceae and obtained from the porcine respiratory tract. These results showed that the Minor group and taxa C, D plus E, and F are distinct phylogenetic groups that are separate from each other and from other members of the family Pasteurellaceae. On the basis of these results, three new species, corresponding to the Minor group, taxa D plus E, and taxon F, are proposed; the names of these new species are Actinobacillus minor (type strain, NM305), Actinobacillus porcinus (type strain, NM319), and Actinobacillus indolicus (type strain, 46KC2), respectively.