In a microorganism that flourishes in hot, acidic vulcanic mud, a previously unknown protein has been discovered by Nijmegen microbiologist Prof. Mike Jetten and his team. The protein breaks down organic sulphur compounds. The gene that codes for this protein has been traced and the protein structure elucidated. That results in a publication in Nature on Octobre 20.
The microorganism Acidianus is an archaeon found in the hot and highly acidic mud of the Campi Flegrei, the ‘burning fields’ of the Solfatara volcano to the north of Naples. It is a unicellular organism that feasts on carbon disulphide (CS2) which it converts with water into the toxic gas H2S (smells of rotten eggs). This chemical conversion process makes Acidianus an interesting candidate for industrial applications, especially in removing CS2 during viscose production from cellulose.
Gene and protein discovered
The Nijmegen researchers who discovered this volcanic resident found out that 30% of its cell is made up bya a special protein, CS2 hydrolase. It is most unusual that such a large part of an organism consists of a single protein.
The researchers tracked down the gene that codes for this protein. They then crystallised the protein and elucidated its structure, which unusually resembles two interlinked doughnuts. The protein was found to have a long tunnel to the active site where the reaction with CS2 takes place. It is very similar to a protein that regulates an ancient and more frequently occurring reaction in nature, namely the formation of carbonate from carbon dioxide and water.
‘Now that we know the gene for the CS2 hydrolase we can find it in far more places and in other microbes. This archaeon lives in that extreme environment and clearly knows how to survive by adapting the protein. We are curious to find out if whether it can also develop in the opposite direction. We will try to simulate accelerated evolution,’ says microbiologist Mike Jetten, the leader of the international team.
Purifying combustion gases
The sulphur microbes were the subject of an applied study funded by the Dutch Technology Foundation STW. Sulphur microbes play an important role in the purification of industrial waste gases but little was known about the best mixture of microbes needed for a quick start up and optimal functioning of the installations. As a result of the study, Jetten’s group can now deliver such a mixture.
In addition to these directly applicable results, the study has also yielded new fundamental insight into the evolution of specific functions in enzymes and the tools nature uses to achieve this.
In collaboration with chemists from Radboud University Nijmegen, the group is now investigating if the protein can be linked to nanostructures. Then the fundamental discovery might yield useful applications.
Prof. Mike Jetten works at the Institute for Water and Wetland Research of Radboud University Nijmegen, the Netherlands.