Streptomyces bacteria. Coloured scanning electron micrograph (SEM) of Streptomyces sp. bacteria. These soil bacteria are responsible for the musty odour of soil. Some Streptomyces bacteria produce antibiotics such as streptomycin. The Streptomyces bacteria share many characteristics with fungi, growing in the soil as a branching network (mycelium) of filaments (hyphae). Magnification: x5,500 at 6x6cm size. x8100 at 4x4"~SQUARE"