PHYLOGENY OF THE PASTEURELLACEAE AS DETERMINED BY COMPARISON OF 16S RIBOSOMAL RIBONUCLEIC-ACID SEQUENCES

Previously, virtually complete 16S ribosomal ribonucleic acid sequence s were determined for 54 strains of species in the family Pasteurellac eae. The sequences for 16 additional strains have been determined, bri nging the total number of strains sequenced to 70. The additional stra ins include: Actinobacillus hominis, A. muris, A. salpingitidis, Paste urella 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 s upported our previously described phylogenetic structure for the famil y Pasteurellaceae. Cluster 1, containing Haemophilus sensu stricto, wa s unchanged. P. mairii was closely related to P. aerogenes and Bisgaar d 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 Pasteur ella sensu stricto. A. hominis was closely related to Actinobacillus s ensu stricto species in Cluster 4A. Bisgaard taxa 5, 8, 9 and P. betty ae fell in Cluster 4B. A. muris was related to P. pneumotropica in Clu ster 5. Haemophilus parainfluenzae strains branched deeply as a 6th cl uster. Bisgaard taxon 14 and P. testudinis formed a 7th cluster which branched deeper than any previously described clusters in the family P asteurellaceae. The branching was extremely complex and taxonomic divi sion of the family into phylogenetically and phenotypically coherent g enera will be difficult.