A New, Wide Host-range, Temperate Bacteriophage (R4) of Streptomyces and its Interaction with some Restriction-Modification Systems

Abstract

A new temperate phage, R4, of Streptomyces was isolated from soil on a restriction-deficient mutant of S. albus G. In its morphology, adsorption properties and growth kinetics R4 resembled other temperate phages of Streptomyces though its requirements for Ca2+ and Mg2+ were higher than usual. It was unable to form plaques above 34.5.degree. C. R4-mediated transduction was not detected. Unlike other Streptomyces temperate phages, R4 had a wide host-range, which correlated better with the absence of detectable class II restriction enzymes than with conventional taxonomic divisions. Many of the sensitive strains [but not, apparently, S. coelicolor A3(2)] could be lysogenized. With the wild-type R4, plaques were obtained on S. albus G only after growth on a restriction-deficient, modification-proficient mutant, and then only at a very low efficiency of plating. All of these plaques were of a mutant type (R4G) which (unlike the parental R4 phage) showed conventional patterns of restriction-modification in the S. albus G (GalGI) and S. albus (SalPI) systems. R4G mutants, but not R4, were sensitive to a restriction-modification system present in 2 S. rimosus strains (2251 and NRRL 2234). DNA from SalGI-unmodified (but not from modified) R4 or R4G was cleaved by SalGI into more than 30 fragments (mean size 1.35 kilobases; summed MW 30.02 .times. 106). R4 DNA was cleaved at 1 site by EcoRI, at 1 site by SalPI (.ident. PstI), and not at all by HindIII or BamHI.