Physiological and Molecular Analysis of the Cyanobacterial CO2 Concentrating Mechanism

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My research examines parts of the photosynthesis process in a group of aquatic microorganisms called cyanobacteria and microalgae. These organisms are important global contributors to the renewal of the oxygen supply in our atmosphere, energy capture and primary productivity and account for about 40% of the carbon dioxide that is fixed by "green organisms". They are the foundation of the food chain in our lakes and oceans and are essential food sources that support the lives of many other organisms.***My specific research examines how cyanobacteria capture carbon dioxide and bicarbonate from their aquatic environment, transport them into the cells and concentrate them for use in photosynthesis. This carbon dioxide concentrating mechanism (CCM) is very interesting since similar processes are not found in most of our crop plants. Many scientists think that we could potentially increase agricultural crop yield if we could transfer the CCM trait from cyanobacteria to selected land plants. How the CCM works in cyanobacteria is the main focus of my research. We are interested in defining the genes and proteins that are required for the CCM, how they are organized in the cell and how they interact with one another to enhance photosynthesis. One unique part of the system is protein structures called carboxysomes. These structures are found in all cyanobacteria, but not in most other organisms. This is where the first biochemical reaction in the photosynthetic pathway of cyanobacteria occurs. Over the past few years we have discovered several enzymes called carbonic anhydrases that are essential to the workings of the CCM in carboxysomes. We are currently exploring how these proteins contribute to photosynthesis, how they regulate the flow of carbon, and how they function at a molecular level. We have identified 4 separate protein sub-complexes in the carboxysomes of cyanobacteria that appear on the surface to perform a similar biochemical function. Through comparative studies we will examine the role of these complexes in specific cyanobacterial species and determine if one or more of the sub-complexes provide a competitive advantage to growth and survival and preferentially enhance photosynthesis.*****