Coral reefs are considered to be one of the most biodiverse ecosystems in the world. Healthy reefs function as a finely tuned system, which excel at capturing and recycling nutrients in nutrient poor (oligotrophic) waters, and their intricate three-dimensional structure allows for niche partitioning that supports spectacular biodiversity and biological productivity. Numerous stressors, including mismanagement of fisheries, coastal pollution, and warming ocean waters have placed corals into a threatened state, with the majority of coral mortality arising from bacterial infection and subsequent disease. We have been working towards gaining a better understanding of the mechanisms that are responsible for coral resilience to disease. Our hypothesis is that bacteria-bacteria "antagonism", or the ability for certain bacteria to outcompete others (including the pathogenic bacteria), plays a fundamental role in coral health. Important to coral survival is their ability to prevent and remove unwanted "pathogenic" bacteria from their surface, a sticky mucus layer, which provides protection to the coral. Our findings suggest that corals are able to shed bacteria through their surface mucus layer, getting rid of unwanted potential pathogens. This discovery was made using a powerful microscope capable of capturing real-time video. In addition to this newly applied video microscopy technique, weÆve also developed a new method for counting bacteria within the mucus layer. This enables scientist to quantity the abundance of bacteria – an important technique when studying disease. To test the hypothesis that bacteria-bacteria antagonism plays a role in coral disease resilience our lab has been able to sequence the genome of two types of bacteria that exhibit very strong antagonism towards other microbes. This antagonism may prove important for "symbiotic", or beneficial microbes ability to prevent pathogenic bacteria from colonizing it. Our most recent findings give insight into the potential molecules called "secondary metabolites" used by these microbes, and we also investigated the enzymes used for breaking down nutrients to digestible molecules, which may allow some microbes to be more successful then others. We suspect that the ability of one microbe to outcompete another within the coral mucus layer is fundamental for the corals selection of symbiotic over pathogenic bacteria. Insight gained by our research, coupled with the methods we have developed, should prove valuable for the field of studies relating to coral reef health and disease. Several publications have resulted from this award and more are in preparation – we list below: M. Garren and F. Azam, "New Method for Counting Bacteria Associated with Coral Mucus", APPLIED AND ENVIRONMENTAL MICROBIOLOGY, p. 6128, vol. 76, (2010). Published, 10.1128/AEM.01100-1 M. Garren and F. Azam, "Corals shed bacteria as a potential mechanism of resilience to organic matter enrichment", The ISME Journal, p. 1159, vol. 6, (2011). Published, 10.1038/ismej.2011.180 M. Garren and F. Azam, "New directions in coral reef microbial ecology", Environmental Microbiology, p. 833, vol. 14, (2011). Published, 10.1111/j.1462-2920.2011.02597 K. L. Rypien, E. E. Allen, S. J. Nam, W. Fenical, P. R. Jensen, K. Penn, F. Azam. Genomic insights into life on a coral: Genome comparison of coral-associated Pseudoalteromonas luteoviolacea and P. flavipulchra. In preparation Y. Zhou, R. Guillemette, F. Azam, "Hydrolytic enzyme activity of mucus and seawater associated with the coral Orbicella annularis". In preparation Last Modified: 10/10/2014 Submitted by: Farooq Azam
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