Molecular cloning of the whole biosynthetic pathway of a Streptomyces antibiotic and its expression in a heterologous host

Abstract

The application of molecular cloning to antibiotic-producing microorganisms should lead to enhanced antibiotic productivity and to the biosynthesis of novel antibiotics by in vitro interspecific recombination^1,2. To allow such approaches, the genes for antibiotic synthesis must be isolated, analysed and perhaps modified. Certain Streptomyces species produce nearly two-thirds of the known natural antibiotics³; the recent development of cloning systems in the genus^4–7 makes it possible to isolate and analyse Streptomyces genes. However, antibiotics are metabolites which require sets of several enzymes for their synthesis and attempts to isolate the corresponding genes have so far yielded clones carrying either individual genes of the set, or only incomplete gene sets^8–11. We describe here the isolation of a large continuous segment of Streptomyces coelicolor DNA which apparently carries the complete genetic information required for synthesis of an antibiotic, actinorhodin, from simple primary metabolites. Not only can the cloned DNA ‘complement’all available classes of actinorhodin non-producing mutants of S.coelicolor but, on introduction into a different host, Streptomyces parvulas, it directs the synthesis of the antibiotic. The tendency for the genes for antibiotic synthesis to be clustered together on the chromosomes of Streptomyces species¹² and the availability of pfasmid vectors which can carry stable inserts of DNA larger than 30 kilobase pairs (kb) and which can be introduced efficiently into Streptomyces protoplasts, suggest that the experiments described have general significance for this area of biotechnology.