Changes in the Population of a Wide Host Range Actinophage Isolated from Thai Soil and Host Streptomycetes in Thai and Japanese Soil

Abstract

We monitored the fate of actinophage Yok-15 isolated from Thai soil, and of its host bacteria, Streptomyces sp. strain 15 (just like Yok-15, both were isolated from Thai soil), S. coelicolor, S. griseus, and S. viridochromogenes in two kinds of Thai and Japanese sterile soil using batch microcosms. Phage Yok-15 had a wide host range and infected 39 important strains of Streptomyces species among the 48 strains tested. In two kinds of Thai soil, phage Yok-15 multiplied to a maximum titer, and then the titer decreased rapidly during incubation with strain 15. However, multiplication of phage YoK-15 was nil during incubation with three other streptomycetes in Thai soil, as well as with all the streptomycetes used in Japanese soil. During incubation with these streptomycetes, the phages decreased more rapidly in titer than did free phages in both Thai and Japanese soil. Therefore, the nature or conditions of the soil and host streptomycetes used affected the survival and multiplication of phages in soil. On the other hand, the survival of host streptomycetes seemed to be more strongly affected by conditions of soil rather than by phage infection.