While the release of CO2 from power generation and other sources into the atmosphere can cause a host of problems including global climate change and ocean acidification, concentrated carbon dioxide represents a rich food source to a cyanobacterium. With energy from sunlight, cyanobacteria can metabolize CO2 via photosynthesis for growth and generation of value-added products. Synthetic biology tools will allow us to genetically alter cyanobacteria to produce greater proportions of their biomass as the most valuable and useful fractions. We are seeking ways to increase the rate at which cyanobacteria are capable of taking up CO2. This is a multi-pronged effort that includes designing new bioreactors for improved microalgal growth, identifying new robust and fast-growing strains,
Genome Sequencing of Cyanothece
Strains of Cyanothece possess the unique ability to temporally separate oxygen-generating photosynthesis from oxygen-sensitive nitrogen fixation. These strains master the co-existence of these incompatible processes through diurnally regulated gene expression. Cyanothece have been isolated from freshwater and marine environments including rice fields in India and Taiwan, as well as costal environments and the open ocean. Our analyses indicate that several members of this genus acquired novel metabolic capabilities while simultaneously retaining archaic metabolic traits.
Hydrogen Production from Cyanothece
Especially when produced biologically, hydrogen can provide a sustainable, carbon-neutral alternative to fossil fuels. Certain microbes possess molecular machines that catalyze hydrogen production. Our work focuses on hydrogen production by Cyanothece, a group of unicellular, diazotrophic cyanobacteria.
Metabolic Modeling and Improvement
Across disciplines, mathematical models of processes are key tools used to understand and improve processes. Our lab is developing new stoichiometric models of cyanobacterial metabolism. Using systems biology data, this type of model takes an organism's genome sequence as a parts list of the molecular machines in the cell. These machines chemically transform inorganic and organic nutrients into all the components of life. The model predicts the relative activity of a cell's molecular machines, and which might be turned up, down, or off via synthetic biology to make more of a particular output such as a biofuel.
Coupled oxidation-reduction (Redox) reactions are required for life, but necessarily generate dangerous reactive oxygen species (ROS). Large concentrations of transition metals, necessary components of photosynthetic reaction centers, within photosynthetic cells can react with and generate new ROS. Photosynthetic organisms have developed extensive antioxidant networks and redox buffering systems to maintain homeostasis while capturing solar energy. In addition to soluble, non-protein antioxidants, Synechocystis 6803 contains enzymatic antioxidants, known as peroxiredoxins. We are particularly interested in the function of one of these proteins, PrxQ, because of its location to the thylakoid lumen.