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J Virol. 1968 July; 2(7): 686-691
Copyright © 1968 American Society for Microbiology. All Rights Reserved.

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

Department of Antibiotics, National Institute of Health, Shinagawa-ku, Tokyo, Japan

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 deoxyribonucleic acid (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 10⁸/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-forming 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.