Antibiotics from gliding bacteria. No. 68. The Ripostatins, Novel Inhibitors of Eubacterial RNA Polymerase Isolated from Myxobacteria.

A new antibiotic, ripostatin, was isolated from the culture supernatant of the myxobacterium, sorangium cellulosum strain So ce377. It is a macrocyclic lactone carbonic acid containing an unsubstituted phenyl ring in a side chain. The antibiotic acts especially on Staphylococcus aureus, but seems not to penetrate most bacteria. The MIC values are in the range of 1 microgram/ml. Ripostatin is an inhibitor of eubacterial RNA polymerase. It interferes with the initiation of RNA synthesis.