Practical procedures for genetic manipulation systems for medermycin-producing Streptomyces sp. AM-7161

Streptomyces sp. AM-7161 is a producer of an aromatic polyketide medermycin with strong antibacterial and antitumor activity. It has been inefficient to perform genetic manipulations in this strain, which heavily hinders the genetic analysis of some interesting problems concerning tailoring modifications in medermycin biosynthesis. Here, condition optimizations of sporulation and mycelium growth of this strain as well as protoplast preparation and regeneration were conducted systematically. Based on these results, protoplast transformation system was established, and two types of foreign plasmids (integrative and auto-replicating) were efficiently introduced into this strain. Additionally, a conjugation system to mediate plasmid transfer between Escherichia coli and Streptomyces sp. AM-7161 was also optimized and established. These results provide the practical procedures to perform more convenient genetic analysis of medermycin biosynthesis in this strain.