Streptomyces coelicolor A3(2) is amongst the best studied representatives of the genus Streptomyces, which is the largest genus within the Actinobacteria. Streptomycetes have a remarkably complex developmental life cycle and the capacity to produce a plethora of natural products. Whilst referred to as S. coelicolor A3(2), this strain is more closely related to Streptomyces violaceoruber ISP5049 than to the type strain for the species, S. coelicolor Müller. However, the name was maintained as it had become the workhorse for genetics and a model for development and antibiotic production. Streptomycetes are multicellular mycelial bacteria that grow as vegetative hyphae, which are compartmentalized via cross-walls. Reproduction occurs when specialized aerial hyphae differentiate into chains of spores. Streptomycetes produce around half of the clinically used antibiotics and other pharmaceutically useful natural products such as anthelmintics, anticancer agents, and immunosuppressives.