The cosmid cloning vector pHC79 has been used to clone fragments of chromosomal DNA from the Streptomyces: S. clavuligerus, S. jumonjinensis and S. katsurahamanus. These strains all produce both the beta-lactam antibiotic, cephamycin and the beta-lactamase inhibitor, clavulanic acid. Although structurally related these two beta-lactams are known to be derived from different biosynthetic precursors. Hybridisation studies and restriction mapping have shown that the gene clusters encoding the two biosynthetic pathways are chromosomally adjacent in these strains, thus creating a 'super-cluster' of genes involved in both the production and enhancement of activity of a beta-lactam antibiotic.