PARENT SESSION
Posters P5D Emerging techniques and systems. Abstracts (731-741)

Quantifying core complexes across taxonomically diverse phytoplankton - relating macromolecular ratios to light and nutrient acclimation. Chris Brown^*,1, Dion Durnford¹, Janice Lawrence¹, Douglas Campbell², Amanda Cockshutt², ¹ University of New Brunswick, Fredericton, NB, Canada² Mount Allison University, Sackville, NB, Canada

ABSTRACT- Photoautotrophs share a set of key processes and pathways, including light capture, conversion of excitation energy to reducing power and ATP, carbon fixation and nitrogen assimilation. These functions are catalyzed by abundant protein complexes that dominate the proteomes of photoautotrophs. We are developing global antibodies and quantitation standards to measure core complexes in populations and mixed communities. Within a given complex, certain peptide sequences of some subunits are well conserved over wide ranges of taxa. We use bioinformatics to design peptide sequence tags to elicit antibodies that recognize all variants of a conserved subunit from each major protein complex of photosynthetic metabolism , regardless of the species of origin. Our goal is to use this suite of global antibodies combined with quantitation standards and robust extraction protocols as a powerful approach to studies of resource allocation, acclimation and metabolic optimization in natural samples or uncharacterized species. In the present study, we grew a taxonomically diverse range of oxygenic photoautotrophs under different steady-state light and nutrient regimes and measured molar quantities of PSI (PsaC), PSII (PsbA), rubisco (RbcL), glutamine synthetase (GlnA), and ATP synthase (AtpB). Different taxa showed distinct allocation patterns under comparable environmental conditions. Some taxa show large plasticity in macromolecular allocations, depending on growth conditions. Within a given taxon, levels and stoichiometries of key complexes suggest taxonomic constraints on resource allocations and physiological performance. Community level allocations to key pools of macromolecules, and thus to key metabolic processes, will thus depend on both the environmental condition and the prevailing taxa present.

KEY WORDS: Global Antibodies, Macromolecular allocations, Phytoplankton, Proteomics