Protease-Sensitive Transfection of Bacillus subtilis with Bacteriophage GA-1 DNA: a Probable Case of Heterologous Transfection

Abstract

The host bacterium of bacteriophage GA-1, Bacillus sp. G1R, was compared with respect to its taxonomic relationship to Bacillus subtilis, B. licheniformis , and B. pumilis. The physiological-biochemical properties of Bacillus sp. G1R are equal to those of B. licheniformis , but the thermal denaturation midpoint of G1R DNA differs by 3 C and the buoyant density by 0.005 g/cm 3 from that of B. licheniformis. Transformation with G1R donor DNA was neither observed in B. licheniformis nor in B. subtilis -competent recipients. Bacteriophage GA-1 shows neither infectivity on B. licheniformis nor on B. subtilis. However, infection of competent B. subtilis cultures with phenol-extracted GA-1 DNA results in the production of infective GA-1 particles. The transfecting activity of GA-1 DNA is destroyed by treatment with proteolytic enzymes. Resistance of transfecting DNA to inactivation by trypsin develops earlier than that to inactivation by DNase. Protease-treated GA-1 DNA competes with transforming DNA to approximately the same extent as does untreated GA-1 DNA, suggesting that uptake of GA-1 DNA is not affected by protease treatment. CsCl density gradient centrifugation reveals that the density of trypsinized GA-1 DNA is 0.004 g/cm 3 greater than that of untreated DNA.