The Streptomycetes are industrially widely used microorganisms due to their ability to produce numerous different chemical compounds. These show very varied effects upon other living systems, and result from profound and subtle biochemical and morphological differentiation during the streptomycete life cycle. It is therefore not surprising that research on the genetics of antibiotic biosynthesis and differentiation in this group is currently progressing rapidly in many countries. Intimately connected with the production of antibiotics is resistance to them; analysis of this is giving further...