Regulated Proteolysis of the Phycobilisome

Cyanobacteria, much like other photosynthetic organisms, adjust their light harvesting apparatus in response to environmental cues. This tuning allows effective light absorbance for the phototrophic metabolism while preventing the deleterious effect of surplus excitation. The phycobilisome, the cyanobacterial pigment antenna, is a supramolecular assembly that may reach 4 MDa. A small protein, NblA, is essential for the degradation of this pigment complex under nutrient limitation. We recently revealed that this small protein associates with phycobilisomes attached to the photosynthetic membranes. We propose that NblA serves a dual function: undermining complex stability and designating the dissociated pigments for degradation (see “Our Projects” for details).

Survival and Death of Aging Cultures

Phytoplankton populations frequently encounter conditions that do not permit cell proliferation e.g. nutrient limitation. Investigation of aging cultures of the cyanobacterium S. elongatus serves to unravel strategies of cell survival as well as cell-death in non-growing cultures. We revealed adaptive plasticity of cell morphology, which is dictated by ambient nutrient status. Additionally, we demonstrated that collapsing aging cultures of S. elongatus produce toxic compounds that effectively kill a large variety of phytoplankton species (see “Our Projects” for details).

Tailoring Cyanobacteria for Biofuel

Environmental as well as economic factors call for sustainable alternatives to the use of fossil fuels. Biofuels derived from arable crops are not cost-effective and the impact of these ‘first generation biofuels’ on food supply and price have raised ethical questions. Photosynthetic microorganisms offer an efficient means for biofuel production that is not associated with the current problems of land-based feedstock. We genetically modified S. elongatus in order to increase accumulation of glycogen, a raw material for bioethanol production.