Studies on relationships between actinophage and variation in Streptomyces: I. Morphology of phage production and lysis in a streptomycete carrying a temperate phage

Abstract

The relationship of phage production to lysis and variation in a streptomycete carrying temperate phage was investigated. Macroscopically, the original isolate, S-77, produced cartilaginous mycelial growth characteristic of Streptomyces. Microscopic examination, however, showed that discrete portions of hyphae were lysed within 48 hours of growth. These lysed portions were widely spaced with the ghost hyphal walls intact so that the mycelial structure and sporogenous habit of the streptomycete were maintained. Variants occurred which ranged from essentially normal-appearing cultures, through lightly sporulated and friable intermediates, to completely asporogenous and mucid cultures.Filtration and electron microscope studies established the presence of phage and showed ghost areas in hyphae as sites of phage release. Phage was found in filtrates of all S-77 variants including the normal-appearing parent type. Incomplete phage particles consisting of collapsed head membranes and of tailless particles were also common. Soft colony types with numerous ghost areas released large amounts of phage. Perfect phage was difficult to find in macroscopically normal cultures where lysed areas were widely spaced. Both normal S-77 and soft variants are either lysogenic or "carriers," since host and phage coexist in an equilibrial state through repeated transfer.It is suggested that the striking variation in morphological and cultural characteristics observed in S-77 results from shifts in the host-phage equilibrium.