GROWTH-CHARACTERISTICS OF V FACTOR-INDEPENDENT TRANSFORMANTS OF HAEMOPHILUS-INFLUENZAE

Haemophilus influenzae is a V factor-dependent species. A plasmid conf erring V factor independence in Haemophilus parainfluenzae and Haemoph ilus ducreyi was transferred to plasmid-free H. influenzae Rd by DNA t ransformation. The growth characteristics of the transformants in a co mplex and a chemically defined medium were compared, and the ability o f several exogenous pyridine nucleotides and precursors to support gro wth was examined. Although the transformants appeared to be V factor i ndependent in a complex medium, in a chemically defined medium they ex hibited both V factor-dependent and nicotinamide-dependent growth. Bec ause of the inability of the plasmid-free H. influenzae Rd to utilize nicotinamide for growth, it was concluded that the genes conferring th is function were plasmid linked. Our results indicate that the V facto r requirement, as it is presently defined, is not suitable to serve as a definitive taxonomic criterion for species determination in the fam ily Pasteurellaceae.