Studies on Streptomyces phage. I. Growth characteristics of the Streptomyces griseus host-phage system.

Within recent years, phages capable of infecting various Streptomyces species have been reported (Saudek and Colingsworth, 1947; Reilly et al., 1947; Koerber et al., 1950; Perlman et al., 1951; and Alexander and McCoy, 1956). Hoehn (1949) and subsequently Gilmour and Buthala (1950) demonstrated that streptomyces phage is indigenous to soil, the natural habitat of the host. The streptomyces host-phage system stands unique among microbial viruses. Of primary significance is the branching, moldlike growth habit of the host. Almost immediately following spore germination (which may form one or more germination tubes) branching of the newly germinated spore occurs. Upon infection with a virulent phage the lytic aspect of the phage-host interaction may be observed by either turbidimetric or microscopic methods. Both approaches are utilized in the present study in demonstrating the lytic feature of the phage infection cycle. The more quantitative aspect, however, of the phage-host interaction lies in following phage growth by means of the one-step growth procedure: adsorption, latent period, and burst size. In this regard it is important to stress the point that a germinated streptomyces spore whether showing one or four germ tubes will plate out as a single colony. Thus the streptomyces cell input value required for accurate burst size values does not represent the true unicellular state. At the present time, this imposes certain restrictions on the extent to which one can apply calculations based on the accurate determination of initial infective centers. It is well, therefore, to recognize that the adsorption, latent period, and burst size data given in the present paper relate to phage infection of a newly germinated spore; the closest facsimile to the unicellular condition.