The myxovalargins, new peptide antibiotics from Myxococcus fulvus (Myxobacterales). I. Cultivation, isolation, and some chemical and biological properties.

Antibiotic activity was isolated from the culture supernatant of the myxobacterium Myxococcus fulvus strain Mx f65. It was active against Gram-positive bacteria (MIC 0.3 approximately 5 micrograms/ml), at higher concentrations also against Gram-negative ones (MIC 6 approximately 100 micrograms/ml), and not at all against yeasts and molds. The activity could be resolved into 4 closely related peptides, the myxovalargins. One of them, myxovalargin A, was by far the most plentiful. The compounds appear to be new antibiotics and seem to interfere with protein synthesis.