New Natural products from a myxobacterium of the recently discovered genus “Aetherobacter”

Abstract

Myxobacteria are a rich source of chemically diverse and bioactive natural products. In particular new myxobacterial genera or families hold great promise as a source of currently unknown secondary metabolites. Recently, we discovered the new myxobacterial genus “Aetherobacter” which is phylogenetically related to Sorangium, one of the most prolific producers of active natural products among myxobacteria. The first Aetherobacter strain that was chemically studied, A. rufus (SBSr003T), was isolated in 2007 from a soil sample containing decaying plant material and the strain also became interesting as source of commercially valuable omega-3 polyunsaturated fatty acids (PUFAs). Further investigations on the secondary metabolites produced by A. rufus led to the discovery of the aetheramides A and B, potent HIV-1-inhibitory and cytotoxic depsipeptides. The second studied Aetherobacter strain SBSr001 was found to exhibit cytotoxicity against a colon carcinoma cell line (HCT-116) and also antibacterial activity against the Gram-positive bacterium Bacillus subtilis. Fractionation based on biological activity and structural features from hyphenated LC-SPE-NMR/-MS yielded the isolation of new compounds including two highly cytotoxic spirangien derivatives. The new structures were established using spectroscopic techniques including 1D and 2D NMR experiments, HR-ESIMS, and chemical derivatization. The new “Aetherobacter” genus will be presented including the isolation and phylogeny of the strain and the structure elucidation of the isolated secondary metabolites together with their biological data.