Expanded Role for Fixation of Carbon Dioxide and Nitrogen in Photosynthetic Bacteria


Primary productivity on Earth depends on the ability of plants and microbes to convert atmospheric CO2 and N2 into biologically useful forms. The enzymatic circuit known as the Calvin Cycle is responsible for the conversion of CO2 into cellular biomass of plants and photosynthetic microbes. Conversion of N2 to ammonia (i.e. nitrogen fixation) is mediated by nitrogenase, an enzyme possessed by only certain microbial species. A new report now shows that the Calvin Cycle and nitrogenase also play a critical role in maintaining the balance of oxidation and reductions processes during growth of Rhodopseudomanas palustris, a metabolically versatile bacterium that can grow in oxygen free environments using a combination of photosynthesis and consumption of organic acids produced by other fermentative microbes. This finding represents a significant advance in our understanding of central metabolic processes of a class of microbes that are both relevant to bioenergy applications and occupy a critical connective role in the global carbon cycle. The new publication is the Inaugural Article for Caroline S. Harwood of the University of Washington as a new member of the National Academy of Sciences.


J. B. McKinlay & C. S. Harwood. “Carbon Dioxide Fixation as a Central Redox Cofactor Recycling Mechanism in Bacteria” 2010 Proceedings of the National Academy of Science (USA). Published Online ahead of print: http://www.pnas.org/content/107/26/11669.