Novel macrocyclic antibiotics: megovalicins A, B, C, D, G and H. I. Screening of antibiotics-producing myxobacteria and production of megovalicins.

New antibiotics belonging to macrocyclic were discovered and named megovalicins A, B, C, D, G and H. The antibiotics were accumulated endogeneously by a newly isolated myxobacterium identified as Myxococcus flavescens. Tank culture of the bacterium for 4 days gave 8.8 g cells/liter on a wet basis, and 4.8, 7.1, 20.0, 0.4, 3.75 and 15.0 micrograms of megovalicins A, B, C, D, G and H respectively were obtained from 1 g wet cells.