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Scientists Unravel 10-Gene Pathway of Sulpho-Glucose Degradation

By discovering sulpho-glycolysis, researchers of the University of Konstanz have revealed an important degradation pathway. Similarly to the sugar glucose, its sulphurous analogue sulpho-glucose is produced by all photosynthetically active organisms. The annual production of sulpho-glucose in nature is estimated at approximately ten billion tons. Researchers of the Department of Biology of the University of Konstanz, in Germany, led by the microbiologists Dr. David Schleheck and Professor Dr. Alasdair Cook, and supported by colleagues from the Department of Chemistry, have now revealed how sulpho-glucose is degraded. The scientists could identify one degradation pathway in the bacterium Escherichia coli (image), the most widely studied bacterial model organism: the sulpho-glycolytic pathway, encoded by ten genes, whose function had remained unknown thus far. The results have now been published in the online edition of Nature. Sulpho-glucose is present in all plants, mosses, ferns, and algae. The degradation pathway, or metabolic pathway, for sulpho-glucose, sulpho-glycolysis, is therefore an important component of the material cycles in ecosystems. As sulpho-glucose is not commercially available, Dr. Thomas Huhn of the neighboring Department of Chemistry synthesised this special form of sugar in sufficient amounts and purity for study. The analytical-chemical studies to give proof of intermediates were conducted via modern mass spectrometry by the doctoral student Alexander Schneider and the chemists Profesor Dr. Christoph Mayer, now at the University of Tübingen, and Professor Dr. Dieter Spiteller. "The excellent collaboration between biologists and chemists was an important aspect of our work. It also highlights the success of the research collaborations established between Biology and Chemistry within the framework of the Graduate Research School Chemical Biology at the University of Konstanz", says Dr. Schleheck. With their microbiological, molecular, and biochemical work, the biologist Dr. Karin Denger and the doctoral students Michael Weiss and Ann-Katrin Felux were able to demonstrate that for sulpho-glycolysis, Escherichia coli does not use its already well-known enzymes for "normal" glycolysis. Instead, ten genes, whose function had remained completely unknown thus far, are responsible for the degradation of sulpho-glucose. Hence, the scientists closed another gap in the knowledge of the most widely studied model organism, Escherichia coli. Additionally, they discovered the new enzymes that catalyse sulpho-glycolysis. It also became apparent that Escherichia coli cannot utilize sulpho-glucose completely, but excretes a sulphurous intermediate, which is degraded by other bacteria in the environment. "Therefore, we were able to demonstrate that sulpho-glucose is completely degraded in nature through the cooperation of several bacteria", explains Dr. Denger. The results of the microbiologists are not only relevant for botany, but also for human biology and zoology, because Escherichia coli is an important and valuable inhabitant of the human and animal intestinal tract, where plant nutrition also provides sulpho-glucose as a so-far overlooked source of nutrients for this bacterium. The genes for sulpho-glycolysis are also present in pathogenic bacteria, such as in Salmonellae. [Press release] [Nature onine]