Project: Bacterial Interactions Underlying Coral Disease Resistance

Extracted from the NSF award abstract:

Despite great strides in recent years uncovering the remarkable genetic diversity of coral-associated bacteria, mitigation and management of coral diseases remains hampered by a lack of understanding of in situ ecological interactions within the microbial community and with exogenous bacteria that underlie coral health and disease. Bacterial attachment and proliferation are critical steps in the infection process, thus inhibiting or preventing colonization and proliferation of pathogens is fundamental to disease resistance. 

Recent research by the investigator demonstrates that corals exposed to organic matter enrichment can become colonized by potential pathogens, but the communities can rebound from such perturbations. Conducting in vitro studies, the investigator found that bacteria-bacteria antagonism is common among coral isolates which suggests it may be a mechanism to resist community shifts and pathogen colonization. It could thus drive resilience within coral-associated microbial communities. In this project the investigator will test these interactions in an in situ context. 

Microbes are critical for the functioning of coral ecosystems at the global scale and, therefore, it is essential that a mechanistic understanding of microbial interactions at the microscale be attained. The following hypotheses will be tested which are designed to elucidate the ecological mechanisms by which bacterial colonization and proliferation in the coral mucus layer (CML) are prevented by microbial interactions: 1) Bacterial community homeostasis in the CML is maintained through the exclusion of potential colonizers 2) Microspatial organic matter hotspots within the coral mucus layer, particularly surrounding zooxanthallae, create loci of intense growth and antagonism 3) Spatially dispersed organic matter inputs overwhelm microscale hotspots and enable pathogens to colonize the CML 

Publications resulting from this research:
M Garren and F Azam. Corals shed bacteria as a potential mechanism of resilience to organic matter enrichment, The ISME Journal, v.6,2011, p. 1159.

M Garren and F Azam. New directions in coral reef microbial ecology, Environmental Microbiology, v.142011, p. 833.

Garren, M; Azam, F. New Method for Counting Bacteria Associated with Coral Mucus, APPLIED AND ENVIRONMENTAL MICROBIOLOGY, v.76, 2010, p. 6128.