In this project an interdisciplinary research team from the University of Hawaii at Manoa, Stanford University, and Rutgers University will study the transcriptomes of Gambierdiscus, Staphylococcus aureus, and Enterococcus in Hawaiian coastal waters - toxin-producing species that pose significant health hazards to humans. Their goal is to elucidate the mechanisms associated with toxin production by Gambierdiscus and inactivation by sunlight of the bacterial pathogen, S. aureus, and the fecal indicator, Enterococcus. Because the transcriptome of an organism reflects the genes that are actively being expressed at any given time, this study, by elucidating levels of messenger RNA expression in the target organisms, should provide valuable insights into the mechanisms responsible for toxin production, responses to stress and/or subsequent bacterial inactivation.
The research program will be organized around four working hypotheses: H1: Production of ciguatoxin by Gambierdiscus reflects the physiological condition of the culture as influenced by temperature, irradiance, and growth phase. H2: High throughput transcriptome analysis from toxin (+) and toxin (-) cultures will allow the identification of genes involved in ciguatoxin production and understanding of the light and nutrient conditions that favor this function. H3: Whereas E. faecalis is susceptible to indirect photoinactivation under exposure to sunlight in seawater, S. aureus is not. This is likely due to the presence of carotenoid pigments within the cells, which are able to quench reactive oxygen species. H4: E. faecalis and S. aureus respond to photo-stress in clear seawater by up-regulating genes that encode for proteins to repair cellular damage and mitigate oxidative stress; this "stressome" will change with increasing exposure to photostress, revealing the stress at which repair is no longer possible.
Broader Impacts: The information that will be gathered in this study is expected to contribute significantly to advancing the field of risk management with respect to recreational water use and seafood consumption beyond reliance on empirical correlations and towards policies that are based on a mechanistic understanding of the threats these organisms pose to human health.