[Determination of the nucleotide composition of Pasteurella multocida strains]

Studied was spectrophotometrically the nucleotide composition of DNA of Pasteurella multocida strains along with studies on the nucleotide base ratio, the molar relations between nucleotide bases, the guanine/cytosine ratio in percent, and the specificity index adenine-tinin/guanine cytosine. The strains used were isolated from birds with various forms of fowl cholera (acute, atypic, and swelling of the wattles), and from calves with bronchopneumonia. Used were also mutants that were streptomycin dependent, obtained through induction with nitrosoguanidine. Close values were established of the nucleotide bases both with the individual groups of Pasteurella strains and with the mutants and their initial strains. The molar relations showed values around a unit, the guanine/cytosine ratio in percent varied from 40.14 to 43,54 and the specificity index varied from 1.25 to 1.49. Data showed that all studied strains and mutants belonged to one species - Pasteurella multocida, on the one hand, and their grouping could not be made on the basis of their nucleotide composition, on the other - contrary to some other indexes, such as biochemical activity, virulence, and behaviour to specific phages.