Of the 5,000 genes studied, nearly 30 percent cycled on and off with changing light and dark periods. These particular genes, the study found, also govern major metabolic processes. Therefore, the cycling of mRNA transcription, Pakrasi said, provides deep insight into the physiological behavior of the organism -- day and night.
During the day, Cyanothece busies itself with photosynthesis. Using energy from sunlight, carbon dioxide from the atmosphere, and water, Cyanothece produces glucose, a sugar it stores in glycogen granules, filling its chemical gas tank. At night, the Cyanothece ramps up production of nitrogenase to fix nitrogen, as expected. Since nitrogen fixation requires a lot of energy, Cyanothece uses the glycogen stored in its chemical gas tank through a process called respiration. Because respiration requires oxygen, the cells conveniently use up this by-product of photosynthesis, likely helping to protect nitrogenase from degradation.
Through this cyclic expression of genes, Cyanothece is essentially a living battery, storing energy from the sun for later use. This feat continues to elude scientists searching for ways to harness sunlight and produce energy on a large scale. With this in mind, a new project for the Pakrasi team seeks to use the machinery of Cyanothece -- its energy storage strategy, its anaerobic conditions that protect important enzymes -- as a biofactory to produce hydrogen from sunlight, the ultimate clean energy source.
|Contact: Gayle Geren|
Washington University in St. Louis