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.