Abstract
Host-produced antibiotics (such as certain polypeptides) are naturally present chemicals recognized as a critical first line of defense against many pathogens including viruses, parasites, and bacteria. These primitive immune factors have been isolated from prokaryotes, plants, invertebrates and vertebrates.5 Environmental stress can down regulate these non-specific immune responses,2,4 and decreased levels of polypeptide antibiotics can greatly increase the susceptibility of animals to infections.1,3 Concern about the deteriorating health of coral reef ecosystems around the globe has fueled interest in determining the immunological defense strategies of Montipora capricornus (an important reef-building hard coral) in attempt to find biomarkers for coral stress and health.
Although numerous publications exist describing the antimicrobial activities of soft corals, there are few publications indicating the presence of antimicrobial activity in hard corals. In the present study, various extraction methods were compared in order to optimize the extraction of antibacterial activity from hard corals.
A hard coral tissue extraction technique was developed that successfully demonstrated the presence of antibacterial activity (against the gram-negative pathogen Escherichia coli) in tissue samples from M. capricornus and Monstrea faeolata hard corals. Initial studies show that the antibacterial activity is resistant to protease treatment (trypsin), and migrates anomalously during native polyacrylamide gel electrophoresis, suggesting that it is probably not proteinaceous and might instead be a small organic molecule.
Studies are currently underway to determine the susceptibility of important coral pathogens to this activity. Knowing this information will help us determine the Minimum Inhibitory Concentration (MIC) levels of the M. capricornus extracts against these coral pathogens. It is hoped that these studies will eventually lead to an effective way of measuring stress in hard corals that can be used to understand what specific environmental factors are causing the global decline of coral reefs.
Acknowledgements
The authors would like to thank the Merck Merial Summer Research Program and The Geraldine R. Dodge Foundation Veterinary Student Fellowship Program for funding portions of this work.
References
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