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Abstract
Summary: While searching for true lysogens among oxytetracycline-producing Streptomyces 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. Electron microscopic examination of RP2 lysates showed that it belongs to group B of Bradley's morphological classification. The rate of RP2 adsorption at 28 °C appeared to be low. The length of the latent period was about 6h and the average burst size about 120 phage particles.
The lysogenic nature of the host-virus system described was established on the basis ofthe following characteristics: spontaneous lysis frequency of 2 × 10−6 per cell, resistance tocuring with phage-specific antiserum, spontaneous curing frequency of less than 0·05% yoand 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
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