2021-03-06 17:59 by TS

Heis­en­berg Pro­fess­or­ship for Dr. Jan-Hendrik Hehem­ann

The dis­cov­ery of a for­got­ten meta­bolic path­way adds a new di­men­sion to the global car­bon cycle

What if poly­sac­char­ide fibers also caused food to sink faster and be di­ges­ted less in the ocean? This is the type of ques­tion that Jan-Hendrik Hehem­ann from MARUM – Cen­ter for Mar­ine En­vir­on­mental Sci­ences at the Uni­versity of Bre­men is look­ing into with his Marine Glycobiology work­ing group, which is a joint group and is loc­ated both at MARUM and the Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy in Bre­men. The team will now also be a part of Fac­ulty 2: Bio­logy / Chem­istry at the Uni­versity of Bre­men and ex­pand on their re­search.

In the ocean, food in the sur­face area is es­pe­cially pro­duced by mi­cro­scopic al­gae. These al­gae syn­thes­ize great quant­it­ies of poly­sac­char­ides from the green­house gas car­bon di­ox­ide. Due to these com­plex car­bo­hydrates, ma­ter­i­als such as cells, min­er­als, and dust stick to­gether and form heavy particles that quickly sink down the wa­ter column. Thus – ac­cord­ing to Hehem­an­n’s hy­po­thesis – poly­sac­char­ides could also be re­spons­ible for a more rapid move­ment of car­bon-rich ma­ter­ial in the ocean, much like the move­ment of food in hu­mans. There­fore, they could help with the stor­age of car­bon in the depths of the ocean and in the mar­ine sed­i­ment.

Bac­teria as teach­ers

“In or­der to be able to an­swer such ques­tions, we need to be able to ex­actly meas­ure poly­sac­char­ides and this poses a prob­lem for us. Poly­sac­char­ides are par­tic­u­larly com­plic­ated mo­lecules that are hard to col­lect. However, bac­teria have found ways of find­ing poly­sac­char­ides and us­ing them as food. They im­ple­ment pro­teins to cap­ture poly­sac­char­ides and en­zymes to di­gest them. We are in­vest­ig­at­ing how bac­teria re­cog­nize poly­sac­char­ides and how their en­zymes work,” ex­plains Jan-Hendrik Hehem­ann. “Every bac­terium, every mi­croor­gan­ism has its very own en­zymes – its own tools – in or­der to cut poly­sac­char­ides. We can use such en­zymes to meas­ures sugar mo­lecules in the sea and thus test the fiber hy­po­thesis.”

The bac­terial en­zymes are re­spons­ible for the break­ing down of sugar com­pounds – they break the large, com­plex poly­sac­char­ides into small, simple mono­sac­char­ide units. These simple sug­ars are, ac­cord­ing to Hehem­ann, easier to meas­ure than poly­sac­char­ides. “By meas­ur­ing simple sug­ars, much like in a dia­betes blood sugar test, we are able to quantify poly­sac­char­ides. Bac­teria are teach­ing us how it is done. This way, poly­sac­char­ides can be quan­ti­fied ac­cur­ately for the first time ever. Ac­cept­ing bac­teria, the smal­lest or­gan­isms on Earth, as a teacher, in or­der to ana­lyt­ic­ally re­cord the global car­bon cycle, is a new ap­proach in mar­ine re­search that has been de­veloped and im­ple­men­ted by our work­ing group.”

Thanks to this ap­proach, it is now pos­sible to meas­ure which sug­ars are most com­mon, which sink into the depths and thus act as a fiber in the ocean. This, in turn, al­lows con­clu­sions to be drawn about the role of poly­sac­char­ides in the car­bon cycle. The ana­lyt­ics and re­search of the new Glycobiochemistry work­ing group make a sig­ni­fic­ant con­tri­bu­tion to the un­der­stand­ing of the ocean as a car­bon store.


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