Intergeneric conjugation in holomycin-producing marine Streptomyces sp. strain M095

Marine Streptomyces are potential candidates for novel natural products and industrial catalysts. In order to set up biosynthesis approach for a holomycin-producing strain M095 isolated from Jiaozhou Bay, China, a genetic transformation system was established using intergeneric conjugation. The plasmid pIJ8600 consists of an origin of replication for Escherichia coli, a phage integrase directing efficient site-specific integration in bacterial chromosome, thiostrepton-induced promoter and an attP sequence. Using E. coli ET12567 (pUZ8002) carrying pIJ8600 as a conjugal donor, while it was mated with strain M095, pIJ8600 was mobilized to the recipient and the transferred DNA was also integrated into the recipient chromosome. The frequency of exconjugants was 1.9+/-0.13x10(-4) per recipient cell. Analysis of eight exconjugants showed pIJ8600 was stable integrated at a single chromosomal site (attB) of the Streptomyces genome. The DNA sequence of the attB was cloned and shown to be conserved. The results of growth and antimicrobial activity analysis indicated that the integration of pIJ8600 did not seem to affect the biosynthesis of antibiotics or other essential amino acids. To demonstrate the feasibility of above gene transfer system, the allophycocyanin gene (apc) from cyanobacterium Anacystis nidulans UTEX625 was expressed in strain M095, and the results indicated heterologous allophycocyanin could be expressed and folded effectively.