Inhibition of restriction in Streptomyces clavuligerus by heat treatment.

Inefficient transformation of Streptomyces clavuligerus protoplasts by DNA from the plasmid pIJ702, isolated from S. lividans, was attributed to restriction in view of the observation that efficient transformation was observed using modified pIJ702 (isolated from S. clavuligerus). The restriction system could be partially inhibited by treating protoplasts at 45 degrees C prior to transformation. This treatment increased the transformation frequencies of pIJ702 DNA by 100-fold and was used to introduce other plasmids into S. clavuligerus.