Transformation ofStreptomyces avermitilis by plasmid DNA

Abstract
Polyethylene glycol (PEG) efficiently mediated the transformation ofStreptomyces avermitilis protoplasts by plasmid DNA to yield 107 transformants per μg of plasmid DNA. Under conditios in which the maximum transformation frequency was observed, the cotransformation frequency exceeded 10%. The number of transformants increased linearly with the amount of DNA and number ofS. avermitilis protoplasts. Relaxed and supercoiled, but not linear DNA transformed protoplasts efficiently. Dimethyl sulfoxide (DMSO)-mediated transformation of protoplasts was 1000-fold less efficient. PEG and, less efficiently, DMSO also mediated the transformation of whole cells ofS. avermitilis by DNA.