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uni'wissen 02-2012 ENG

minous plants build a protective environment for the bacteria in their roots by nature. In order to reduce the bacteria’s dependency on this envi- ronment, the scientists are counting on another solution: directed evolution. “We place the bacte- ria under evolutionary pressure,” says Einsle, “and tell them what to do for us.” On culture plates, the scientist is growing numerous bacte- ria that can only cover their need for nitrogen by producing nitrogenase. An advantage of this method is that bacteria have short generation times. Einsle then adds a small amount of O2, damaging the nitrogenase and thus preventing further growth. Eventually, however, mutations start taking place that can enable one or two out of every million bacteria to continue growing anyway, because their modified nitrogenase is more tolerant of oxygen. At this point, the bio- chemist understands and possesses a bacterium that can do exactly what he wanted it to do. Now he just needs to introduce this bacteria into high- er organisms, because the ultimate goal is to en- able this process to take place in plants. Einsle knows that this is a big challenge: “It will be an exciting journey that will lead us far into unchart- ed territory.” Future Microorganisms Will Break Down Harmful Gases Einsle has another reason to be optimistic: The goal of his research project “N-ABLE” is not just to give plants the ability to supply them- selves with N2, thus obviating the need for indus- trial fertilizer. In addition, the Freiburg researcher wants to produce modified bacteria that break down the harmful N2O gas before it is released into the atmosphere. Laughing gas is released even without synthetic fertilizer – for instance by industrial plants and through geological process- Prof. Dr. Oliver Einsle studied biology in Con- stance and earned his PhD in biochemistry and bio- physics at the Max Planck Institute of Biochemistry (MPIB) in Martinsried. After a year as a postdoctoral researcher at the MPIB, he worked from 2001 to 2002 at the California Institute of Technology in Pasadena, USA. From 2003 to 2008 he had a position as junior professor of protein crystal- lography at the University of Göttingen. Since 2008 he has served as professor of biochemistry at the Fac- ulty of Chemistry, Pharma- cy, and Earth Sciences of the University of Freiburg. Einsle is a member of the Cluster of Excellence BIOSS Centre for Biologi- cal Signalling Studies of the University of Freiburg and the American Chemical Society. His main research interests are the structure and function of membrane proteins and metallopro- teins. Photo: Seeger es. Einsle thus plans to use the same method of directed evolution he has developed for nitroge- nase to analyze the process of nitrous-oxide re- ductase. The ultimate goal is to use this enzyme to produce modified bacteria that N2O can use as a source of energy. The bacteria would then break down the gases from the air. “The topic has attracted the attention of vari- ous organizations and many political bodies,” ex- plains Einsle. Among other things, he is receiving a starting grant from the European Research Council worth 1.64 million euros in the next five years. In addition, the International Panel on Cli- mate Change of the United Nations recently called on scientists to find a solution to these problems at a conference on global climate change. Further Reading Lü, W./Du, J./Schwarzer, N. J./Gerbig-Smentek, E./Einsle, O./Andrade, S. L. A. (2012): The formate channel FocA exports the products of mixed-acid fermentation. In: Proceedings of the National Academy of Sciences of the United States of America 109, p. 13254 – 13259. Spatzal, T./Aksoyoglu, M./Zhang, L./Andrade, S. L. A./Schleicher, E./Weber, S./Rees, D. C./ Einsle, O. (2011): Evidence for interstitial carbon in nitrogenase FeMo cofactor. In: Science 334 (6058), p. 940. Pomowski, A./Zumft, W. G./Kroneck, P. M. H./ Einsle, O. (2011): N2O binding at a [4Cu:2S] copper-sulfur cluster in nitrous oxide reductase. In: Nature 477 (7363), p. 234 – 237. 19