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Bacterial symbionts have long been suspected to be the true producers of many drug candidates isolated from marine invertebrates. Sponges, the most important marine source of biologically active natural products, have been frequently hypothesized to contain compounds of bacterial origin. This symbiont hypothesis, however, remained unproven because of a general inability to cultivate the suspected producers. However, we have recently identified an uncultured Pseudomonas sp. symbiont as the most likely producer of the defensive antitumor polyketide pederin in Paederus fuscipes beetles by cloning the putative biosynthesis genes. Here we report closely related genes isolated from the highly complex metagenome of the marine sponge Theonella swinhoei, which is the source of the onnamides and theopederins, a group of polyketides that structurally resemble pederin. Sequence features of the isolated genes clearly indicate that it belongs to a prokaryotic genome and should be responsible for the biosynthesis of almost the entire portion of the polyketide structure that is correlated with antitumor activity. Besides providing further proof for the role of the related beetle symbiont-derived genes, these findings raise intriguing ecological and evolutionary questions and have important general implications for the sustainable production of otherwise inaccessible marine drugs by using biotechnological strategies. F or almost 30 years, symbiotic bacteria have been discussed as the likely true producers of numerous natural products isolated from marine invertebrates (1). Particularly suggestive of a bacterial origin is the similarity of many compounds from sponges, tunicates, or bryozoans to complex polyketides and nonribosomal peptides, two groups of metabolites that are otherwise known exclusively from microorganisms (2, 3). Into these structural families fall some of today's most promising drug candidates, such as discodermolide, bryostatin 1, aplidine, and ET-743 (4). The existence of producing symbionts could have far reaching consequences for the development of sustainable, fermentation-based sources of invertebrate-derived drug candidates, almost all of which are currently inaccessible in large amounts. Several studies have tried to pinpoint the producers by using cultivation (5), cell separation (6), immunolocalization (7), or in situ hybridization (8) approaches. However, as none of these methods have so far provided unambiguous results, the true origin of the compounds still remains an enigma. We have recently used a genetic strategy to provide insights into natural product symbiosis in terrestrial insects (9). Rove beetles of the genera Paederus and Paederidus are the source of the highly active antitumor polyketide pederin (Fig. 1), which they use as chemical defense (10). We isolated a set of putative pederin biosynthesis genes (9, 11) from the metagenome of Paederus fuscipes beetles and traced them to a bacterial symbiont with the closest relationship to Pseudomonas aeruginosa (12). The genes encode a mixed modul...

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The peer-reviewed marine pharmacology literature from 2009 to 2011 is presented in this review, following the format used in the 1998–2008 reviews of this series. The pharmacology of structurally-characterized compounds isolated from marine animals, algae, fungi and bacteria is discussed in a comprehensive manner. Antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral pharmacological activities were reported for 102 marine natural products. Additionally, 60 marine compounds were observed to affect the immune and nervous system as well as possess antidiabetic and anti-inflammatory effects. Finally, 68 marine metabolites were shown to interact with a variety of receptors and molecular targets, and thus will probably contribute to multiple pharmacological classes upon further mechanism of action studies. Marine pharmacology during 2009–2011 remained a global enterprise, with researchers from 35 countries, and the United States, contributing to the preclinical pharmacology of 262 marine compounds which are part of the preclinical pharmaceutical pipeline. Continued pharmacological research with marine natural products will contribute to enhance the marine pharmaceutical clinical pipeline, which in 2013 consisted of 17 marine natural products, analogs or derivatives targeting a limited number of disease categories.