Preparation of Competent Single-Cell Suspensions of Mycoplasma hominis tets and Mycoplasma salivarium tets for Genetic Transformation to Tetracycline Resistance by DNA Extracted from Mycoplasma hominis tetr

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Abstract
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 rrnl, respectively, to resistance. The transformants were selected on agar medium containing 10 µg of tcrracycline/ml. Some transformants were resistant also to 20 µg of tetracycline /rnl, 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 µg of tetracyclinejml was bacteriostatic. Prototype experiments employing mixtures of strains that were tetr and tets (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 MgCI 2 and CaCI2, while Mycoplasma orale type 2 was inactivated. During DNA extraction different quantities of DNA formed insoluble precipitates with protein, thus preventing quantitative experiments.