Temperate Bacteriophages for Streptomyces coelicolor A3(2) Isolated from Soil

Abstract

S U M M A R YThree phages, isolated from soil samples collected in different localities, produced turbid plaques with a characteristic morphology on Streptomyces coeZicoZor ~3 ( 2 ) . Surviving growth from the plaques was lysogenic: when isolated and purified it was resistant to lysis by the homologous phage and released phage at a low frequency during growth. The three phages were homoimmune. The chromosomal attachment site of one of the prophages, VP5, was mapped in a position between hisE and cysD -that is, in a region devoid of standard markers -on the circular linkage map of the host, by crossing defective lysogens with sensitive strains. The host range of VP5 was restricted; only certain strains belonging to the S. coelicolor (S. violaceorkber) group were attacked. VP5 gave rise to clear-plaque mutants, incapable of lysogenizing the host, at a spontaneous frequency of I O -~, which was increased by U.V. irradiation and by hydroxylamine mutagenesis ; the clear-plaque mutants were incapable of lysing strains carrying the wild-type prophage. Electron microscopy showed that VP5 belongs to group B of Bradley's morphological classification.

Characterization and Persistence of Actinophage RP2 Isolated from Streptomyces rimosus ATCC 10970

“…The fact that these lose their ability to lysogenize sensitive cells but are still unable to lyse strains carrying the wild-type prophage suggests, by analogy with phage h (Hershey, 1971), that these mutations affect some steps of the lysogenization process. Similar mutants have been isolated from the S. coelicolor A3(2) temperate phages $C3 1 and VP5 (Lomovskaya et al, 1970;Dowding & Hopwood, 1973). However, clear-plaque mutants of Bacillus subtilis phage SP10, which does not establish a stable relationship with the host, were reported (Kawakami & Landman, 1968).…”

“…Lomovsks?ya et al (1972) and Dowding & Hopwood (1973) observed that only a few per cent of S. coelicolor A3(2) spores plated gave rise to colonies releasing phage. The fact that about 30 to 40% of the R7 cells plated produced colonies releasing phage may be explained in terms of the faster growth of the lysogenic strain than the sensitive strain.…”

“…Its morphology and double-stranded DNA content place it in group B of Bradley's morphological classification (Bradley, 1967). It is a tadpoleshaped particle, like most other actinophages (Welsch, 1969;Hopwood et al, 1973;Korn et al, 1978), apart from the tail-less actinophage $17 (Bacq & Horne, 1963) and rod-like nocardiophage described by Azarowitz et al (1954).…”

“…However, the genetically well-characterized strain Streptomyces coelicolor A3(2) (Sermonti, 1969;Hopwood et al, 1973) appears to be the only actinomycete in which the genetic control of lysogeny has been investigated. Lornovskaya et al (1970) were the first to describe a temperate phage isolated from S. coelicolor A3(2), while Dowding & Hopwood (1973) reported the isolation of the free virion VP5, capable of lysogenizing the same strain.…”

Methods for the Direct Isolation and Enumeration of Actinophages in Soil

“…Phages for many bacterial genera may be readily isolated from most soils by enrichment of the soil with the potential host (Adams, 1959;Billing, 1969;Willoughby et al, 1972;Dowding, 1973;Dowding & Hopwood, 1973;Zachary, 1974), with nutrients (Reanney & Marsh, 1973;Casida & Liu, 1974;Tan & Reanney, 1976;Germida & Casida, 1981) or with both host and nutrients (Newbould & Garrard, 1954;Retinskaya & Rautenstein, 1960). Phages thus isolated have been widely used in biochemical, genetic and taxonomic research.…”