Blooms of the toxic dinoflagellate Gymnodinium breve occur in coastal waters throughout much of the Gulf of Mexico, but are especially problematic along the Florida coast where these annual events last at least 3 months and exact a large toll on the regional economy with losses estimated at about $20 million per episode. The current project is aimed at beginning to elucidate the role of algicidal bacteria in promoting the decline and dissipation of G. breve red tides along the Florida Gulf coast. The hypothesis that algicidal bacteria specific for G. breve are present in microbial assemblages indigenous to the Florida Gulf coast is tested using a straightforward, previously successful, approach which involves isolating bacteria that prohibit or interfere with the growth of G. breve. Isolation media used select for bacteria requiring G. breve derived organics, a characteristic of several previously described algicidal bacteria. A formulation supporting growth of bacterial strain 5N 3, a strain lethal to G. breve is also tested. Bacterial isolates with algicidal activity specific for G. breve are characterized with classical and molecular techniques. The latter will provide small subunit (ssu) rRNA sequence data, which will be used during a follow up study to design and develop oligonucleotide probes for these bacterial strains. The work proposed herein represents the first attempt to investigate the association between algicidal bacteria and HABs in U.S. waters. This project is anticipated to result in the isolation and identification of a bacterial strain(s) which inhibits specifically the growth of the Florida red tide dinoflagellate, G. breve. Sequencing of the ssu rRNA gene and the subsequent development of rRNA probes will provide a means by which to track populations of these bacteria in controlled (e.g., mesocosms) as well as natural systems, and thus to better assess their involvement in promoting bloom decline. Finally, the knowledge gained from this study is an essential first step in critically evaluating the potential use of algicidal bacteria as a means of controlling or regulating HABs, a process currently underway in other countries severely impacted by algal blooms (e.g., Japan)
