Decoding "Dark Matter"? The Discovery of A New Type of Methanogenic Archaea

Recently, the anaerobic microbial innovation team of the Biogas Science Research Institute of the Ministry of Agriculture and Rural Affairs (hereinafter referred to as "Biogas Science Institute"), in collaboration with Wageningen University in the Netherlands and other institutions, discovered and isolated and cultivated a new type of methanogenic archaea. The relevant results were published in Nature.

Methanogenic archaea are one of the oldest life forms on Earth, appearing on Earth about 3.46 billion years ago. Methanogenic archaea play an important role in the current natural ecosystem of the Earth. For example, methanogenic archaea contribute 70% of global methane emissions. Methane is the second largest greenhouse gas after carbon dioxide, and its warming effect is 28 times that of carbon dioxide, accounting for 20% of the global greenhouse effect. In addition, methanogenic archaea participate in the process of converting underground organic matter into methane and carbon dioxide, and play a key role in the global carbon cycle. Methanogenic archaea are responsible for fixing 2% of the world's carbon every year.

The traditional view is that methanogenic archaea belong to the phylum Euryarchaeota in the Archaea domain. In recent years, based on some basic research, the academic community has proposed that non-Erythroarchaeota methanogenic archaea are widely distributed in nature, and speculated that in addition to producing methane, these new archaea also have the potential for non-methane metabolism such as fermentation growth and sulfur oxidation.

"Methanogenic archaea are a type of microorganism that grows by producing methane to obtain energy, but if they also have non-methane metabolic capabilities such as fermentation growth and sulfur oxidation, the role of methanogenic archaea in the global element cycle will change," said Cheng Lei, the corresponding author of the paper and chief scientist of the anaerobic microbial innovation team of the Institute of Biodiversity. So far, these archaea are in a "dark matter" state and there has been no pure culture, so this view has not been confirmed by research.

The "dark matter" state refers to the fact that scientists have obtained the genome of archaea through sequencing technology, but the presence of genes does not mean that they will be expressed, that is, they may not necessarily work in the environment. Therefore, to confirm this point of view, it is necessary to separate the archaea, obtain a single strain, that is, a pure culture, and then conduct physiological function experiments to verify its gene expression.

In the opinion of Dong Xiuzhu, a researcher at the Institute of Microbiology, Chinese Academy of Sciences, this study reports the first new evolutionary group of methanogenic archaea that does not belong to the traditional ones, expanding the scope of methanogenic archaea. Moreover, this type of archaea that produces methane by reducing methyl substances with hydrogen and their metabolic pathways are widely distributed in oxygen-deficient underground environments around the world, indicating that they make an important contribution to global methane emissions.