The biosynthetic gene cluster for the β-lactam carbapenem thienamycin in Streptomyces cattleya

Abstract

β-lactam ring formation in carbapenem and clavam biosynthesis proceeds through an alternative mechanism to the biosynthetic pathway of classic β-lactam antibiotics. This involves the participation of a β-lactam synthetase. Using available information from β-lactam synthetases, we generated a probe for the isolation of the thienamycin cluster from Streptomyces cattleya. Genes homologous to carbapenem and clavulanic acid biosynthetic genes have been identified. They would participate in early steps of thienamycin biosynthesis leading to the formation of the β-lactam ring. Other genes necessary for the biosynthesis of thienamycin have also been identified in the cluster (methyltransferases, cysteinyl transferases, oxidoreductases, hydroxylase, etc.) together with two regulatory genes, genes involved in exportation and/or resistance, and a quorum sensing system. Involvement of the cluster in thienamycin biosynthesis was demonstrated by insertional inactivation of several genes generating thienamycin nonproducing mutants