Marine Sponge Extracts Research Articles

Allelopathic activities of sponge extracts

Although there is anecdotal evidence for allelopathic interactions between benthic invertebrates engaged in spatial competition, only a few studies have established the involvement of chemical agents in field experiments. We have developed a technique in which crude organic extracts of marine sponges were incorporated into hard, stable gels that serve as a substratum for overgrowth by invertebrates in the field. Overgrowth organisms were secured to the center of assay plates and allowed to grow laterally over control gels and gels containing a crude organic sponge extract that was volumetrically equivalent to the concentration found in sponge tissues. Extracts of 20 species of Caribbean sponges were assayed in Florida using 3 overgrowth sponges: Tedania ignis, Lissodendoryx isodictialis, and Haliclona hogarthi. In addition, extracts of the sponge Aplysilla longispina were assayed in North Carolina using the tunicate Diplosoma listerianum as the over- growth organism. The allelopathic effects varied between extracts of different sponge species, but were consistent across overgrowth organisms. Of the sponge extracts tested, 30% inhibited sponge growth (Amphimedon compressa, Aplysilla longispina, Aplysina cauliformis, Dysidea etheria, Ectyo- plasia ferox, and Phorbas amaranthus), while 15% promoted overgrowth (Agelas wiedenmeyeri, Geodia gibberosa, and Halichondria sp.). The remaining 55% of sponge extracts had no effect on sponge growth. The technique described herein represents a more ecologically relevant method than past techniques for assaying the allelopathic properties of extracts of marine organisms. Moreover, this study provides evidence that sponge metabolites may act as allomones by preventing overgrowth of some sponge species, and as both allomones and kairomones by enhancing overgrowth of others.

High-throughput screening of small molecules in miniaturized mammalian cell-based assays involving post-translational modifications

Fully adapting a forward genetic approach to mammalian systems requires efficient methods to alter systematically gene products without prior knowledge of gene sequences, while allowing for the subsequent characterization of these alterations. Ideally, these methods would also allow function to be altered in a temporally controlled manner. We report the development of a miniaturized cell-based assay format that enables a genetic-like approach to understanding cellular pathways in mammalian systems using small molecules, rather than mutations, as the source of gene-product alterations. This whole-cell immunodetection assay can sensitively detect changes in specific cellular macromolecules in high-density arrays of mammalian cells. Furthermore, it is compatible with screening large numbers of small molecules in nanoliter to microliter culture volumes. We refer to this assay format as a 'cytoblot', and demonstrate the use of cytoblotting to monitor biosynthetic processes such as DNA synthesis, and post-translational processes such as acetylation and phosphorylation. Finally, we demonstrate the applicability of these assays to natural-product screening through the identification of marine sponge extracts exhibiting genotype-specific inhibition of 5-bromodeoxyuridine incorporation and suppression of the anti-proliferative effect of rapamycin. We show that cytoblots can be used for high-throughput screening of small molecules in cell-based assays. Together with small-molecule libraries, the cytoblot assay can be used to perform chemical genetic screens analogous to those used in classical genetics and thus should be applicable to understanding a wide variety of cellular processes, especially those involving post-transitional modifications.

Biosynthetic studies of marine lipids-xxix. Demonstration of sterol side chain dealkylation using cell-free extracts of marine sponges

Cell-free extracts of eight marine sponges were used in biosynthetic studies to examine the course and scope of sterol side chain dealkylation.