Macro-photograph of a colony of the soil bacterium Streptomyces viridichromogene. Streptomyces species are natural producers of a number of antibiotics, including streptomycin. A member of the Actinomycetes group, they share many characteristics with the fungi. The bacteria grow in the soil as a branching network of filaments, known as a mycelium (yellow). They also produce aerial mycelium, from the tips of which develop chains of spores (white & grey). When the spores are mature, they rupture and are dispersed on the wind.