Phylogeny of the Pasteurellaceae as determined by comparison of 16S ribosomal ribonucleic acid sequences.

Previously, virtually complete 16S ribosomal ribonucleic acid sequences were determined for 54 strains of species in the family Pasteurellaceae. The sequences for 16 additional strains have been determined, bringing the total number of strains sequenced to 70. The additional strains include: Actinobacillus hominis, A. muris, A. salpingitis, Pasteurella bettyae, P. mairii, P. testudinis, and Bisgaard taxa 2, 3, 5, 6, 7, 8, 9, 13, and 14 (2 strains). A phylogenetic tree was constructed based upon sequence similarity using the Neighbor-Joining method. The additional sequence information and phylogenetic analysis generally supported our previously described phylogenetic structure for the family Pasteurellaceae. Cluster 1, containing Haemophilus sensu stricto, was unchanged. P. mairii was closely related to P. aerogenes and Bisgaard taxon 6 was related to H. somnus in Cluster 2. A. salpingitidis and Bisgaard taxa 2, 3, 7, and 13 fell in Cluster 3 which contains Pasteurella sensu stricto. A. hominis was closely related to Actinobacillus sensu stricto species in Cluster 4A. Bisgaard taxa 5, 8, 9 and P. bettyae fell in Cluster 4B. A. muris was related to P. pneumotropica in Cluster 5. Haemophilus parainfluenzae strains branched deeply as a 6th cluster. Bisgaard taxon 14 and P. testudinis formed a 7th cluster which branched deeper than any previously described clusters in the family Pasteurellaceae. The branching was extremely complex and taxonomic division of the family into phylogenetically and phenotypically coherent genera will be difficult.