The sorangicins, novel and powerful inhibitors of eubacterial RNA polymerase isolated from myxobacteria.

A new antibiotic, sorangicin, was isolated from the culture supernatant of the myxobacterium, Sorangium (Polyangium) cellulosum strain So cel2. It is a macrocyclic lactone carbonic acid and is produced in two structural variants, sorangicins A and B. In addition small quantities of the respective glycosides, sorangiosids A and B, may be found. The antibiotic acts mainly against Gram-positive bacteria, including myocobacteria, with MIC values between 0.01 and 0.1 microgram/ml, but at higher concentrations (MIC 3 approximately 30 micrograms/ml) Gram-negatives are also inhibited. Yeasts and molds are completely resistant. The new antibiotic is a specific inhibitor of eubacterial RNA polymerase which it blocks, however, only if added before RNA polymerization has started.