actinomycete Streptomyces griseus , found in soil.
It was among the first antibiotics discovered (1943, by Selman Waksman ), after penicillin , gramicidin, and tyrocidine. The first antibiotic effective against {{link=tuberculosis">tuberculosis , it interferes with the tubercle bacillus's ability to synthesize certain vital proteins. It still has some use in combination with penicillin for treating endocarditis and with tetracyclines in the treatment of plague, tularemia, and brucellosis.