Miuraenamides A and B, novel antimicrobial cyclic depsipeptides from a new slightly halophilic myxobacterium: taxonomy, production, and biological properties.

A slightly halophilic myxobacterial strain, SMH-27-4, was isolated from nearshore soil and shown to belong to a new myxobacterium genus based on phylogenetic analysis. This slowly-growing myxobacterium produced the novel antibiotic depsipeptides miuraenamides A and B. Their physico-chemical properties and molecular formulas, C34H42N3O7Br and C34H42N3O7I, were determined. Miuraenamides A exhibited potent and selective inhibition against a phytopathogenic microorganism, Phytophthora sp., and moderate inhibition against some fungi and yeasts, but was ineffective against bacteria. Both of the metabolites inhibited NADH oxidase at IC50 values of 50 microM, suggesting, like beta-methoxyacrylate-type antibiotics, the electron transfer system of the mitochondrial respiratory chain as the cellular target.