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Oceanography Seminar

March 20, 3:00pm - 4:15pm
Mānoa Campus, MSB 100

Thomas S. Bibby
National Oceanography Centre
Southampton Ocean and Earth Sciences
University of Southampton

“Photosynthetic efficiency: characterization in marine systems and optimization for biotechnological applications”

Abstract: The efficiency at which absorbed light is converted into biomass is a fundamental parameter in determining the productivity of ocean systems. Many marine phytoplankton have evolved to be very efficient at absorbing light, using a diverse range of light-harvesting pigment-protein complexes. However, the photosynthetic energy conversion efficiency is low, especially when iron is limiting – the molecular basis of this is poorly understood. Here the photosynthetic macromolecular responses of phytoplankton communities in situ and within nutrient addition experiments over a seasonal cycle in the sub-polar North Atlantic are presented. Iron stress resulted in significant increases in the cellular ratios of total chlorophyll to the photosynthetic catalysts, providing evidence that phytoplankton accumulate energetically uncoupled chlorophyll-binding complexes under these conditions. We estimate that such iron-stress-induced chlorophyll-binding proteins contribute ~30% of the total chlorophyll in the studied system. Photosynthetic energy conversion efficiency has also been identified as the central bottleneck in the commercial realization of developing photosynthetic microbes as sources of biofuels and other high-value products. We show that, by using single-cell sorting capabilities of flow cytometers in combination with random mutagenesis of wild-type populations and transcriptomics, we can select, isolate and characterize cells with improved energy conversion efficiency. The study represents a high-throughput pipeline for the development of microalgae species currently lacking genomic and/or genetic tools necessary for targeted strain improvement and thus expands the diversity of marine phytoplankton that can be considered as realistic candidates for biofuel production.

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Oceanography, Mānoa Campus

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