Isolation and characterization of two types of actinophage infectingStreptomyces scabies

摘要

Two types of actinophages, ϕS and ϕL, were isolated from soil samples by usingStreptomyces scabies, a potato scab pathogen, as indicator strain. The phages were partially characterized according to their physicochemical properties, plaques and particles morphology, and their host range; this varied from narrow (for ϕS) to wide (for ϕL). The adsorption rate constants of the ϕS and ϕL were 3.44 and 3.18 pL/min, and their burst sizes were 1.61 and 3.75 virions per mL, respectively. One-step growth indicated that ϕS and ϕL have a latent period of 1/2 h followed by a rise period of 1/2 h. The temperate character of these phages was tested in other isolates ofStreptomyces. Four of the phages (ϕSS3, ϕSS12, ϕSS13 and ϕSS17) were identified as temperate phages, since they were able to lysogenize SS3, SS12, SS13 and SS17. ϕSS3, ϕSS12 and ϕSS13 were homoimmune, and they were heteroimmune with respect to ϕSS17. The restriction barriers of lysogenic isolates (SS12, SS13 and SS17) interfered with the blockage of plaque formation by phages (ϕSS12, ϕSS13 or ϕSS17) propagated on them, about 75% of lysogenic isolates had restriction systems. The exposure of the lysogenic isolates (SS12, SS13 and SS17) to UV-irradiation prevented the possible restriction barriers of these isolates so that these barriers could be overcome.