We want to keep methane out of our atmosphere as much as possible: it is a powerful greenhouse gas, more than 25 times stronger than carbon dioxide. To limit methane emissions, the researchers looked at the MCR enzyme, which can determine whether methane is released into the air or recycled into carbon dioxide in microorganisms.
Not much was known about the specific microorganisms studied in this research (ANME), because they are difficult to cultivate in the laboratory. Until now, only one MCR structure had been studied, originating from a microbial mat collected in the Black Sea.
Methane cycle
'Since both methane-consuming (ANME) and methane-producing microorganisms (methanogens) depend on MCRs, we wondered whether they function in the same way in both directions of the methane cycle,' says project leader Tristan Wagner of the Max Planck Institute for Marine Microbiology in Bremen. 'To understand the differences between the MCRs of ANMEs and methanogens, we needed an image of the enzyme.' Researchers from Radboud University supplied the MCRs from two different freshwater samples.
Same MCR
In these enrichments, researchers from Radboud University and the National Museum of Natural Sciences in Madrid analysed the microbial communities, which revealed the presence of MCRs.
Subsequent analysis showed that MCRs from both freshwater and saltwater ANME were very similar to the MCRs in methanogens, despite their metabolic differences. ‘The MCR enzyme is involved in both methane production and methane consumption, only working in the opposite direction,’ explains Welte of Radboud University.
Climate
This study underlines the importance of understanding enzymes in their natural context. 'By knowing exactly how this works, we can understand the natural methane filter better,' concludes Welte. 'If we understand that methane filter better, we can use it in the future to reduce greenhouse gas emissions from the waste sector, for example.'