POLYPHASIC ANALYSIS OF STRAINS OF THE GENUS CAPNOCYTOPHAGA AND CENTERS-FOR-DISEASE-CONTROL GROUP DF-3

A polyphasic approach was used to determine the relationships between well-characterized reference strains representing all seven Capnocytop haga species. One Centers for Disease Control (CDC) group DF-3 strain, a presumed relative of the genus Capnocytophaga, and 15 field isolate s were included as well. Fourteen isolates were assigned to named Capn ocytophaga species, all of which could be differentiated by means of w hole-organism protein electrophoresis, A separate position was occupie d by the CDC group DF-3 strain and by one field isolate representing a novel Capnocytophaga species. The phylogenetic position of each taxon was determined by means of 16S rRNA sequence analysis. A considerable genotypic heterogeneity within the genus Capnocytophaga was detected in spite of the minimal phenotypic differences. Comparative 16S rRNA s equence analysis revealed that CDC group DF-3 is not a close relative of the capnocytophagas but constitutes a separate genus that clusters together with Bacteroides forsythus and Bacteroides distasonis, two ge nerically misclassified Bacteroides species. The degree of protein sim ilarity correlated with our and published DNA-DNA binding values. Perc entage 16S rRNA similarity values of greater than 97% did not guarante e conspecificity. All Capnocytophaga strains had very similar fatty ac id contents characterized by significant amounts of 14:0, 15:0 iso (gr eater than 55%), 16:0, 16:0 3OH, and 17:0 iso 3OH, PCR-mediated DNA fi ngerprinting allowed discrimination of most species, although some str ains could not be classified efficiently because of DNA polymorphisms.