[Physical mapping of actinophage Streptomyces coelicolor A3(2). VI. The use of deletion mutants of actinophage phi C31 for construction of phage vectors].

Nonessential region responsible for G function has been identified in theta C31 phage genome by means of deletion mutants. The mutant phenotype is expressed upon theta C31 phage propagation in Streptomyces albus G strains differing in functioning of restriction and modification systems. Based on their increased resistance to EDTA, deletions were located in theta C31 delta 10 and theta C31 delta 65 phage mutants. Data are presented on physical mapping of nonessention region of theta C31 phage. The total length of this region is 24.1% of the overall length of DNA molecules. The DNA segment of 19.1% of the whole genome contains overlapped deletions. Theta C31 actinophage is proposed to be used as a cloning vector for Streptomyces. Various deletion mutants obtained, with the capacity of about 3 thousands base pairs may serve as "insertion vectors". The presence of the stretched nonessential genome region allows to use theta C31 phage as a "replacement vector". Then, insertion of foreign DNA to replace the EcoRI--C fragment of theta C31 DNA of 6.4 x 10(3) base pairs is possible. The phages comprising hybrid molecules may be selected for G and Lyg phenotypes.