Characterization and Persistence of Actinophage RP2 Isolated from Streptomyces rimosus ATCC 10970

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Abstract
While searching for true lysogens among oxytetracycline-producing S. rimosus strains, free phage particles were detected and isolated from a liquid culture of S. rimosus ATCC 10970 (R7). The actinophage, designated RP2, appears to be a typical temperate DNA phage producing turbid plaques on the sensitive strain S. rimosus R6. EM examination of RP2 lysates showed that it belongs to group B of Bradley''s morphological classification. The rate of RP2 adsorption at 28.degree. C appeared to be low. The length of the latent period was about 6 h and the average burst size about 120 phage particles. The lysogenic nature of the host-virus system described was established on the basis of the following characteristics: spontaneous lysis frequency of 2 .times. 10-6/cell, resistance to curing with phage-specific antiserum, spontaneous curing frequency of < 0.05% and immunity to superinfection with the homologous phage. Clear-plaque mutants of RP2, which failed to lysogenize sensitive cultures, arose at a frequency of 10-5.