Molecular Insights Into a Dinoflagellate Bloom Imply Bacterial Cultivation

Weida Gong1, Nathan Hall2, David Schruth1, Hans W Paerl3 and Adrian Marchetti4, (1)University of North Carolina at Chapel Hill, Marine Sciences, Chapel Hill, NC, United States, (2)University of North Carolina, at Chapel Hill, Institute of Marine Sciences, Morehead City, NC, United States, (3)University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC, United States, (4)University of North Carolina, at Chapel Hill, Department of Marine Sciences, Chapel Hill, NC, United States
Abstract:
In coastal waters, an increase in frequency and intensity of algal blooms worldwide has recently been observed primarily due to eutrophication, with further increases predicted as a consequence of climate change. In many marine habitats most impacted by human activities, efforts have been made to prevent conditions that promote harmful algal blooms, or HABs, although progress is limited, due in part to our current lack of understanding of the environmental and cellular processes that promote and propagate these blooms. Comparative metatranscriptomics was used to investigate the underlying molecular mechanisms associated with a dinoflagellate bloom in a highly eutrophied estuarine system. Here we show that under bloom conditions, there is increased expression of metabolic pathways indicative of rapidly growing cells, including energy production, carbon metabolism, transporters and synthesis of nucleic acids and cellular membrane components. In addition, there is a prominence of highly expressed genes involved in synthesis of membrane-associated molecules, including those for the production of glycosaminoglycans (GAGs), which may serve roles in nutrient acquisition and/or cell surface adhesion. Biotin and thiamine synthesis genes also increased expression along with several cobalamin biosynthesis-associated genes that suggests processing of B12 intermediates by dinoflagellates. The patterns in gene expression observed are consistent with bloom-forming dinoflagellates eliciting a cellular response to facilitate interactions with their surrounding bacterial consortium, possibly in an effort to cultivate for enhancement of vitamin and nutrient exchanges and/or direct consumption. Our findings provide potential molecular targets for HAB detection and remediation efforts.