California Sea Grant College Program

Actinomycetes are high G+C content Gram-positive bacteria with an unparalleled ability to produce diverse secondary metabolites. These bacteria, which are best known from soils, have been studied extensively by the pharmaceutical industry and account for a disproportionately large amount of the $25.3 billion annual global sales of microbially derived pharmaceuticals. In recent years however, the yield of new lead compounds from common soil-derived actinomycetes has diminished significantly, thus providing incentive to broaden the search for new metabolites to include actinomycetes that occur in the sea. The goals of this proposal were to gain a better understanding of actinomycete diversity in the ocean and their ability to produce unique secondary metabolites. The approach taken was to develop cultivation techniques specific for marine actinomycetes and to assess the diversity of cultured strains using molecular systematics. Representatives of various taxonomic groups were then cultured, extracted, and the extracts assessed for biological activity and the presence of novel secondary metabolites. Special efforts were made to focus on a unigue group of chemically prolific marine actinomycetes that we discovered and called MAR2 or "Marinospora".