Deoxyribonucleic acid base composition of the genus Lactobacillus.

Deoxyribonucleic acids of 45 strains of Lactobacillus and 5 strains of Bifidobacterium which had been analyzed for base composition by chromatographic means were examined at equilibrium in a CsCl density gradient. Regression analysis showed that there have been systematic errors involved in the estimation of guanine plus cytosine (GC) content by the chemical method, and that the relation between buoyant density and base composition is indeed linear and best fitted by the equation GC = 10.309 (rho-1.662), which compares well in slope with the equation of Schildkraut, Marmur, and Doty. With the improved data obtained in this study, the specific groupings of the species of both genera were reevaluated.