Cyanobacteria are photosynthetic organisms that have evolved to efficiently harvest solar energy, thus being a matter of great biotechnological interest, using what seem to be infinite resources, water and solar energy, to convert carbon dioxide into complex molecules (glycogen, proteins, lipids, secondary metabolites, etc). Following advances in synthetic biology and metabolic engineering, we now have tools to create specifically-designed photosynthetic factories. However, modifying a living cell almost always bears the trade-off of being detrimental to its growth. This competition between anabolic and product formation pathways is a crucial topic of research in the photobiological biofuels production field. Indeed, how the cell regulates the partitioning of carbon between biomass production and the synthesis of product of interest is still not well understood. We previously reported that the removal of a major carbon sink can redirect the carbon flow towards the production of target metabolites under stress conditions: when deprived of nitrogen, the mutant strain of the cyanobacterium Synechocystis sp. PCC6803 incapable of glycogen synthesis (∆glgC) excrete the organic acids alpha-ketoglutarate and pyruvate for several days, without increasing cell biomass, making it a simplified system to study carbon partitioning in photosynthetic organisms. Recent evidences have led us to suggest that the ratio of alpha-ketoglutarate/pyruvate can be differentially altered and adaptable to environmental conditions, suggesting that carbon partition might be tightly linked to this ratio. The ATP/NADPH ratio has also been hypothesized to regulate photosynthesis and carbon partition. Following new insights from transcriptomics, proteomics, and metabolomics results, we are currently using various approaches to measure target metabolites pools alongside the ATP/NADPH ratio and the cell redox state using fluorescence in the wild-type and mutant ∆glgC strains under different conditions. Understanding carbon partitioning will require achieving an integrative view of the given state of the cell at various levels, by means of omics data and physiological studies.

Regulation of photosynthetic carbon partitioning in a cyanobacterium

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.