Composition of Bacterial Communities Associated with Acroporid Coral Mortality Event in the Florida Keys during 2003
Shawn W. Polson1,2, Shawn M. McLaughlin3, and Cheryl M. Woodley1,2
1 Marine Biomedicine and Environmental Sciences Center, Medical University of South Carolina, Charleston, SC
2 NOAA/National Ocean Service, Charleston, SC
3 NOAA/National Ocean Service, Oxford, MD
During the Spring and Summer of 2003, mortalities of acroporid corals were observed along the length of the Florida Keys from Biscayne National Park in the north to Dry Tortugas National Park in the south. Mortalities were characterized by irregularly shaped lesions of dead coral surrounded by a border of sloughing tissue. In some areas the mortality was also marked by apparent bacterial aggregates, evident under light microscopy, occurring at increasing frequency in corals showing signs of disease. This study is designed to survey microbial communities associated with corals sampled in the affected areas in order to identify potential pathogenic agents and to characterize the manner in which microbial communities shift in the diseased state. Ground coral tissue and mucus samples were collected from healthy and diseased colonies along the length of the affected area and were used as template for PCR amplification of microbial 16S rRNA. Thin-sections of coral with and without visible aggregates, as well as laser capture microdissection (LCM) aggregates were also used as template. PCR products were cloned and sequenced. Analysis of sequence homology indicates the presence of at least 14 orders of bacteria across three phyla represented in diseased tissues. Bacterial aggregates isolated by LCM showed a marked increase in bacteria of the genus Pseudomonas. Ongoing research is expanding on these results and attempting to determine localization of bacteria within the observed aggregates.