Abstract
A new procedure for transformation of Amycolatopsis (Nocardia) mediterranei LBG A3136 was developed. The method makes use of polyethylene glycol and alkaline cations and enables direct transformation of the A. mediterranei mycelium with high efficiency: more than 10(6) transformants per microgram of DNA were obtained. Transformation of A. mediterranei is stimulated by the ionophore antibiotic valinomycin and abolished by arsenate and p-chloromercuribenzenesulfonate. pMEA123, a vector based on the indigenous plasmid pMEA100 and containing the erythromycin resistance gene, was constructed.