PREPARATION OF COMPETENT SINGLE-CELL SUSPENSIONS OF MYCOPLASMA-HOMINIS-TET(S) AND MYCOPLASMA-SALIVARIUM-TET(S) FOR GENETIC-TRANSFORMATION TO TETRACYCLINE RESISTANCE BY DNA EXTRACTED FROM MYCOPLASMA-HOMINIS-TET(R)

DNA extracted from Mycoplasma hominis (Sprott strain), resistant to 100 μg of tetracycline/ml, transformed M. hominis strain H29 and Mycoplasma salivarium strain S9, which are sensitive to 2.5 and 5.0 μg of tetracycline/ml, respectively, to resistance. The transformants were selected on agar medium containing 10 μg of tetracycline/ml. Some transformants were resistant also to 20 fig of tetracycline/ml, a finding confirming that transformation occurred between homologous and heterologous species and that resistance is stepwise and controlled by several genetic loci. Medium containing 10 fig of tetracycline/ml was bacteriostatic. Prototype experiments employing mixtures of strains that were tetr and tet8 (tetracycline-resistant and tetracycline-sensitive, respectively) demonstrated that tetr mutants and transformants formed typical fried-egg colonies when mixtures containing not more than 109 mycoplasmas were spread on tetracycline agar plates. No mutants to tetracycline resistance were detected. Both M. hominis and M. salivarium were competent after treatment with MgCl2 and CaCl2, while Mycoplasma orale type 2 was inactivated. During DNA extraction different quantities of DNA formed insoluble precipitates with protein, thus preventing quantitative experiments. © 1979 by The University of Chicago.