Discovery challenges beliefs about origins of marine-derived climate-cooling gas
By: Communications
New research has identified a novel enzyme that has significant implications for our understanding of global sulphur cycling, marine biogeochemistry, climate-cooling gas production and the potential for life on other planets.
The collaborative research, from the University of East Anglia (UEA) and the Ocean University of China (OUC), challenges the long-held belief that a compound called dimethylsulfoniopropionate (DMSP) is the sole source of a climate-cooling gas called dimethylsulfide (DMS), which is known as the smell of the seaside.
Last year it was revealed that Nasa's James Webb Space Telescope may have detected DMS on a planet 120 light years away from Earth.
This was hailed as a breakthrough and a potential sign of life on another planet, as until now the view was that on Earth, at least, DMS is only produced by life.
Co-lead author Professor Jonathan Todd, of UEA’s School of Biological Sciences, said: “Our discovery not only potentially reshapes our understanding of marine sulphur cycling but also broadens the scope of potential biosignatures for extraterrestrial life.
“The enzyme we identified could be a key player in the generation of the climate-active gas dimethylsulfide in Earth’s Oceans.”
Study Biological Sciences at UEA
Co-first author and PhD student at UEA, Chuang Sun, said: “The MddH enzyme generates DMS via a pathway that was not thought to be important in marine systems, where most DMS is made.”
Co-lead author Professor Xiao-Hua Zhang, of OUC’s College of Marine Life Science, said: “Microbes containing and expressing the mddH gene, identified here, are abundant in marine systems. Thus, our work has the potential to change the belief that DMSP is the only significant route to the production of the climate-cooling gas DMS.
"Furthermore, because the system identified here generates DMS from hydrogen sulphide and methanethiol which are gases common in anaerobic settings, it is possible that a system like this could be responsible for the DMS recently tentatively seen on the distant planet K2-18B and that was billed as a sign of life.”
First author Dr Yunhui Zhang, of OUC’s College of Marine Life Science, said: “The environment on the planet K2-18B is aquatic and anoxic potentially with lots of hydrogen sulphide around.
“This environment, akin to some hydrothermal vents, might provide a suitable environment for the microbial methylation of hydrogen sulphide and methanethiol to generate DMS.”
Background:
Every year, billions of tonnes of DMSP are produced in the Earth's oceans by marine microorganisms, helping them to survive by protecting against various stresses like changes in salinity, cold, high pressure, and oxidative stress.
Diverse microbes produce enzymes to cleave DMSP and yield DMS. This is believed to be the major route for global DMS production. The work here highlights that other bio-routes to DMS from hydrogen sulphide and methanethiol may also be important. Hydrogen sulphide and methanethiol are reactive gases often highly abundant in anoxic environments.
This work is important because large amounts of DMS are released into the atmosphere, where DMS oxidation products help form clouds which reflect sunlight away from the Earth, effectively cooling the planet.
This natural process is essential for regulating the Earth’s climate and is also hugely important for the global sulphur cycle, representing the main route by which sulphur from the oceans is returned to land.
UEA and OUC established the Sino-UK Joint Research Centre to promote cutting-edge research and teaching in marine and ocean science.
Its previous research identified the bloom-forming Pelagophyceae algae as potentially abundant and important producers of DMSP.
This latest research was a collaboration between UEA and OUC, with contributions from Qingdao Marine Science and Technology Center and the Tobacco Research Institute of Chinese Academy of Agricultural Sciences.
The work was supported by National Natural Science Foundation of China, the Chinese Scolarship Council, the Fundamental Research Funds for the Central Universities, the Scientific and Technological Innovation Project of Qingdao Marine Science and Technology Center, the UK Biotechnology and Biological Sciences Research Council (BBSRC), the UK Natural Environment Research Council and the Leverhulme Trust.
‘An S-methyltransferase that produces the climate-active gas dimethylsulfide is widespread across diverse marine bacteria’ is published in Nature Microbiology.
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