Factors Affecting Infection of Protoplasts with Deoxyribonucleic Acid of Actinophage PK-66

Abstract

To establish a method for transmission of genetic materials in the genus Streptomyces, the conditions of infection of protoplasts of S. kanamyceticus by actinophage PK-66 DNA were studied. The protoplasts of Streptomyces were prepared by treatments with lysozyme and trypsin. The infectivity of the phage DNA was enhanced by the presence of NaCl in the medium. The optimal concentration of the protoplasts for infection with DNA was 7 x 107 to 4 x lO^/ml. A proportional relationship was found between the infectivity and the DNA concentration within a certain range. The maximal production of mature phage was achieved after 19 hr. of incubation. The number of phage propagated in the infection mixture reached 104 plaque-form ing units per ml under the appropriate conditions. The phage DNA infected not only protoplasts prepared from S. kanamyceticus but also those prepared from S. violaceoniger and S. acidomyceticus, which were resistant to intact phage PK-66.