SPECIFICITY OF DNA UPTAKE IN GENETIC TRANSFORMATION OF GONOCOCCI

Genetic transformation of gonococci to streptomycin resistance was inhibited by homologous DNA or by DNA from related Neisseriae, but not by high concentrations of heterologous DNAs. Gonococci were capable of adsorbing large quantities (up to about 50 μg per 108 cells) of both homologous and heterologous DNA, which could not be eluted by strong shearing forces. Treatment with externally added DNase removed virtually all the heterologous DNA while a small fraction of the homologous DNA, not influenced by the presence of excess heterologous DNA, remained cell-bound in a form resistant to nuclease treatment. Competing homologous DNA suppressed nuclease-resistant binding. These findings suggest that gonococci have two types of DNA binding components at their surface. Competence of gonococci for genetic transformation undergoes a rapid decay if the cells are incubated with homologous (but not with heterologous) DNA. © 1979.