Monday, August 12, 2013
Pavilion (Sheraton San Diego)
The conditions under which bacteria grow in the marine environment are very different from those traditionally used for natural product discovery. This in part may explain the disparity between the large number of biosynthetic pathways observed in bacterial genome sequences relative to the number of secondary metabolites that can be detected in culture extracts. In an effort to induce the expression of “silent” biosynthetic pathways, we have developed a microcosm cultivation method in which sediment-derived marine bacteria are cultured in unamended seawater and sand. These static cultures generate surprisingly high amounts of cell biomass by deriving nutrients entirely from autoclaved natural seawater and marine sediment. Initial studies using the marine actinomycete Salinispora arenicola (strain CNS-991) revealed good growth and secondary metabolite production following 45 days of microcosm cultivation. The analysis of crude organic extracts revealed the production of antibiotics in the rifamycin class at higher relative proportions than observed in traditional shake flask culture. This represents the first observation of antibiotic production by Salinispora species in unamended seawater/sediment media. This technique provides opportunities to explore more natural cultivation conditions as a method to induce secondary metabolite production and thereby improve the rate of new compound discovery.