The focus of this project is on the interrelationship between photosynthetic carbon assimilation and nitrogen fixation in a cyanobacterium, Synechococcus. Dr. Spiller plans to examine the uptake and kinetics of carbon assimilation in the organisms and the effect of carbonic-anhydrase inhibitors on bicarbonate utilization. It is also planned to examine the mechanism of oxygen exchange, using glucose in light and dark, and bicarbonate under photosynthetic conditions. The use and availability of glucose as compared to carbon dioxide to support nitrogen fixation will be examined. Experiments are also planned in which use is made of energy-transfer inhibitors in order to examine the role played by the electrochemical potential of protons in dark:light transients of N-fixing Synechococcus cells. The cyanobacteria are structurally simple organisms, often unicellular and often free-living, which have a remarkable ability to make use of the nitrogen gas in the environment in a manner that higher animals and plants cannot do. These bacteria, like most plants, are capable of harnessing radiant energy in the form of sunlight and producing organic carbon-containing compounds by photosynthesis. Inorganic carbon is taken in and chemically manipulated to provide appropriate carbon compounds that can combine with newly fixed nitrogen. The photosynthetic process involves high rates of oxygen production, and this is a potential problem for the cyanobacteria because the enzymes that fix nitrogen are highly sensitive to oxygen. Dr. Spiller's project makes use of a simple cyanobacterium that is well suited for attempting to understand in detail how carbon metabolism and nitrogen metabolism are united in a successful partnership in this organism.
