Microscale Co-cultivation of Marine Bacteria: an Approach for Production of Unique Natural Products

Marine bacteria have been an exciting source of novel and therapeutically relevant chemistry. Genomic evaluations of marine bacteria have revealed unexpressed, or cryptic, biosynthetic gene clusters under standard laboratory growth conditions. Unfortunately, cryptic biosynthetic genes impede the discovery of novel antibiotic scaffolds necessary to combat the rising incidence of antibiotic resistance. We hypothesize that co-cultivation of marine invertebrate-associated bacteria may provide interspecies interactions to coax cryptic biosynthetic genes to produce natural products. To investigate many sets of interactions, we developed a microscale (500µL) co-cultivation approach using LC/MS-based untargeted metabolomics to detect natural product production in co-cultures versus monoculture controls. Onaka et al. showed that mycolic acid-containing bacteria can induce pigment formation and antibiotic production when co-cultured with Streptomyces sp.¹ Inspired by this work, we co-cultured Streptomyces sp. with mycolic acid-containing bacteria. Furthermore, we are the first to report co-cultivation of Micromonospora sp. with mycolic acid-containing bacteria. Co- and monoculture extracts were screened to identify antibiotic production exclusively in co-culture. Subsequently, co-cultures producing antibiotic activity were analyzed using LC/MS-based principal component analysis (PCA) to graphically represent metabolic differences between co- and monocultures. Our co-culture approach allows for the rapid detection of antibiotic leads from cryptic biosynthetic genes.

¹Onaka, H.; Mori, Y.; Igarashi, Y.; Furumai, T. Appl. Environ. Microbiol. 2011, 77, 400 – 406.