Viral re-wiring of cyanobacterial photosynthesis

Oxygenic photosynthesis is a fundamental biological activity. As well as oxygenating the atmosphere, it is also the basis of all food chains and global carbon cycling via the direct fixation of carbon dioxide (CO2) into organic matter. Cyanobacteria are the oldest and numerically most abundant oxygenic phototrophs on Earth. My lab has recently established that viruses infecting cyanobacteria (cyanophage) inhibit host CO2fixation during infection [1, 2]. This inhibition of the dark reactions of photosynthesis (i.e. CO2fixation) contrasts with cyanophage maintaining the photosynthetic light reactions (i.e. electron transport) as a means to provide energy for phage replication [2, 3]. However, the mechanism by which cyanophage inhibit CO2fixation is unknown. We have recently identified a cyanophage protein (CinI) which we hypothesise directly interacts with the key CO2fixing enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) rendering the enzyme inactive. RuBisCO is one of the most abundant proteins in the biosphere, catalysing the carboxylation and cleavage of ribulose-1,5- bisphosphate (RuBP) into two molecules of 3-phosphoglycerate and is found in all three domains of life: bacteria, archaea and eukaryotes. Using cutting edge molecular genetics, biochemical and live-cell imaging approaches this project will thus seek to understand the inhibition mechanism, and in so doing provide new biological insights into how CO2fixation is mechanistically controlled, potentially allowing for its exploitation in energy generation e.g. through cyanobacterial/algal bio-photovoltaics.

The project requires a multidisciplinary skill set combining molecular genetics, microbiology, biochemistry (protein over-expression, protein crystallisation) and live cell imaging (via GFP-YFP protein interaction studies).