streptomyces are medically important, as they produce antifungals, antiparasitic drugs, antivirals, antitumorals, anti-hypertensives, immunosuppressants and antibiotics. different species of streptomyces are used to produce different antibiotics. over 500 species of "streptomyces" bacteria have been described. for example, widely studied "s. griseus" was the first to be used in production of an antibiotic streptomycin, while "s. avermitilis" as a source of avermictin. another well-studied species, "s coelicolor", is widely used in genetic studies. overall, streptomyces produce over two-thirds of the clinically useful antibiotics of natural origin, such as tetracycline, neomycin and chloramphenicol.