Lichtgedanken 05

Rubrik 47 05 | LICHT GEDANKEN Sulphur can be found everywhere on earth: in the atmosphere, in the oceans, and on land. Its forms of appearance are connected in a cycle. »Sulphur is in- itially reduced from the mineralic form sulfate and transferred into organic compounds; it is then passed around by organisms until it finally reaches the atmosphere and is then oxidized to sul- fate before it is returned to the land and oceans via rain«, says chemist Prof. Dr Georg Pohnert, explaining the global sulphur cycle. Together with colleagues from the USA, he and his team from the Institute of Inorganic and Analytical Chemistry have discovered a »shortcut« in this well-known cycle. It is tiny organisms in ocean plankton that are responsible. »We’ve found that certain single-cell algae and bacteria, which form part of the plankton in the sea, produce a chemical compound with the complicated name Dimethyl- sulphoniopropionate, or DMSOP for short«, says Pohnert. »This has allo- wed us to deduce valuable information about the global sulphur cycle, and we can now provide a new explanation for huge quantities of sulphur flow in the cycle. Even though one microalga only produces negligible quantities of the compound, we’re talking about sever- al tera-grams in total, so several billion kilograms a year.« This is because sing- le-celled algae are extremely active in the world’s oceans. The findings made by Jena’s chemists thus give better un- derstanding of Earth’s sulphur cycle, which offers important knowledge for atmospheric and climatic models. Sophisticated system as stress protection for algae However, the findings do not just help us to better understand the sulphur cycle. The scientists found one rea- son for the production of DMSOP by investigating how the algae adapt to their environment. »These single-cel- led organisms are permanently moving around in the sea, and so they’re cons- tantly exposed to different salt contents and oxidative stress«, explains Pohnert. »The new compound now shows how this stress can be balanced out through a sophisticated system of chemical reac- tions.« One way of doing this is by pro- ducing and breaking down highly polar organic molecules. DMSOP plays a key role here. The Jena-based scientists, whose work is supported by the »ChemBioSys« (see p. 10) collaborative research centre, in- vestigated water samples from diffe- rent ocean regions for their research. The aim was to find out whether the production of the sulphur-compound was a global phenomenon. »We found DMSOP in all investigated samples taken from the Arctic to the Mediterra- nean«, explains Prof. Pohnert. »So, pro- ducers of the sulphurous compound can be found everywhere.« These new results have provided with important information about the fun- ctioning of microbial communities in the ocean. The results are also rele- vant for possible concrete applications. »More and more algae are being grown in aquaculture to produce animal feed, foodstuffs and energy. That’s why it is important to fully understand their metabolism«, says chemist Pohnert. »These latest insights have once again revealed the incredibly complex and effective system that is hidden away in plankton.«  Contact Prof. Dr Georg Pohnert Institute of Inorganic and Analytical Chemistry Lessingstraße 8, D-07743 Jena, Germany Phone: +49 36 41 9-48 170 Email: georg.pohnert@uni-jena.de www.chemgeo.uni-jena.de/iaac Original publication: The metabolite dimethylsulfoxonium pro- pionate extends the marine organosulfur cycle, Nature (2018), DOI: 10.1038/s41586- 018-0675-0 Image left: Prof. Dr Georg Pohnert inspects algae cultures that are bred in a special container. Image right: The graphcal representation of our globe by the space agency NASA shows the amount of chlorophyll, which is pro- duced by marine algae in the oceans. In ad- dition, the tiny algae produce huge amounts of the sulphurous substance DMSOP.