[Genetic characteristics of a new phage resistance trait in Streptomyces coelicolor A3(2)]

Phage resistance was investigated in the system of Streptomyces coelicolor A3(2) and phi C31 actinophage. Resistance of A3(2) strain to phi C31 was shown to involve a novel mechanism responsible for the arrest of phage intracellular growth in the whole cell population. The phage resistance character designated Pgl+ (for "phage growth limiting") is determined by a gene located on the A3(2) chromosome. The gene (pgl) controls phage "modification" which results in an inability of phage to lyse lysogenize Pgl+ host. Instability of the Pgl+ character was revealed. Pgl+ strains segregate Pgl variants at a high frequency, the majority of Pgl strains reverting to the initial Pgl+ phenotype with the same high frequency. Reversible Pgl+ in equilibrium Pgl transitions are a common feature of A3(2) cell population.