Characteristics of Streptomyces griseus strains resistant to phage

Characterization of the virulent actinophage S2

The virulent actinophage S2 isolated from soil infects Streptomyces hygroscopicus 6599, S. lividans 66, and S. levoris 1331. Morphology of S2 was studied by electron microscopy. Influence of growth medium and temperature on multiplication of S2 has been studied qualitatively. S2 is more sensitive to UV irradiation on strain 66 than on 1331. In contrast to UV, hydroxylamine mutagenesis delivered 9 stable ts mutants which belong to 3 complementation groups. Most of the ts mutations isolated on 1331 were found to be host dependent, 8 of 9 mutants were found to be able to grow at 40 degrees C on strain 66 but none of them on 1331. Moreover 2 of the mutants were found to be much more heat sensitive in 6599 than in 1331, as indicated by the changes in half-life temperatures. The latent period of S2+ depends on temperature and germination state of the spores. Under optimal conditions we found 140 min. Ts2 and ts7 have been classified as a late and ts17 as an early mutant.

RIFAMYCIN. XXXIII. ISOLATION OF ACTINOPHAGES ACTIVE ON STREPTOMYCES MEDITERRANEI AND CHARACTERISTICS OF PHAGE-RESISTANT STRAINS

Five actinophages highly specific for Streptomyces mediterranei were isolated from lysed broth cultures. Studies were performed on the effect of plating conditions on plaque formation. The development of phage-resistant strains of S. mediterranei not only eliminated the phage but also significantly increased rifamycin yields. The phage-resistant cultures proved to be more unstable than the original sensitive strain. Maintenance of the cultures as frozen vegetative mycelium assured culture stability and reproducibility of the results. Strict aseptic precautions throughout the laboratories and fermentation areas did not eliminate the danger of phage infection; effective control was obtained only with the introduction of resistant strains. S. mediterranei phages proved to be highly specific for calcium as an adsorption cofactor; addition of calcium-sequestering agents to sensitive mycelium completely prevented its lysis by the phage. The resistant strains developed were capable of adsorbing the phage and of releasing it without multiplication upon aging of the mycelium. No marked morphological, cultural, or biochemical differences were found among the various phage-resistant strains.

Electron microscope study of the multiplication of the actinophage affecting Streptomyces griseus

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