Transduction and transformation of plasmid DNA in Streptomyces fradiae strains that express different levels of restriction.

We constructed nonrestricting strains of Streptomyces fradiae blocked in different steps in tylosin biosynthesis. Plasmid transformation frequencies were 10(3)- to 10(4)-fold higher and bacteriophage plating efficiencies were 10(4)- to 10(8)-fold higher in the nonrestricting strains than in the restricting strains. The efficiencies of transduction of plasmid pRHB101 in S. fradiae strains varied by over 1,000-fold, depending on growth conditions, and optimum transduction frequencies were obtained when cells were grown to mid-exponential phase at 39 degrees C. Under these conditions, restricting and nonrestricting strains were transduced at frequencies that differed by only two- to fivefold.