Archaea are here! Hydrogen-powered cars may be powered by "microorganisms" in the future

Tuchong Creative

As environmental problems such as global warming intensify, clean new energy has developed rapidly. In addition to the solar and wind energies that are familiar to everyone, hydrogen energy fueled by hydrogen is also a very important clean energy source, because the combustion of hydrogen only produces precious water, and there is no carbon dioxide emission at all. However, the manufacture, storage and transportation of hydrogen have high technical difficulties and high costs. Now, a new discovery by biologists may bring a new technical path, allowing archaea to help us produce hydrogen.

What are archaea? On the surface, they are very similar to bacteria, and are both very small single-celled organisms, so they were once called archaea for a long time. Because scientists at the time believed that they were older than bacteria. However, with the development of genome sequencing technology in recent years, more and more evidence has shown that these so-called archaea are actually not the same kind of organisms as bacteria. Therefore, they were renamed archaea by biologists and became a separate archaea domain. In contrast, there is the bacterial domain and the eukaryotic domain. All kinds of macroscopic organisms that we can see in our daily lives, such as plants, animals, including humans ourselves, and some microorganisms such as fungi, all belong to the eukaryotic domain.

The reason why there are so many twists and turns in the understanding of archaea is that they are too similar to bacteria and not very similar to eukaryotic cells. For example, eukaryotic cells have a formed nucleus surrounded by a nuclear membrane, while archaea and bacteria do not have a formed nucleus, so archaea and bacteria are collectively called prokaryotes. In addition, the cell size of archaea and bacteria is significantly smaller than that of eukaryotic cells. The genomes of archaea and bacteria are circular, while the genomes of eukaryotic cells are assembled into complex chromosomes.

However, as human beings' understanding of biology deepens to the molecular level, they find that some core systems of archaea are more like those of eukaryotes. For example, the DNA of both archaea and eukaryotes is wrapped around a class of proteins called histones, which improves the controllability of structural stability, while bacteria do not have such a mechanism. At a deeper level, the transcription mechanism, DNA replication mechanism, DNA repair mechanism of archaea, and the enzymes involved in these mechanisms are closer to the systems of eukaryotes and are quite different from the systems of bacteria.

In addition, archaea have some unique characteristics of their own. For example, the composition of their cell membrane is different from that of bacteria and eukaryotes.

It is precisely because of this cross-entangled similarity that scientists find it difficult to sort out the evolutionary origin relationship between archaea, bacteria and eukaryotes. A theory that is currently widely accepted is that eukaryotes are the result of the accidental combination of archaea and bacteria. However, this theory also has some unexplained links that still need to be studied.

Regardless of their origins, on Earth today, archaea live in harmony with bacteria and us eukaryotes. Early studies found that archaea were mainly located in some extreme environments, such as high-pressure and high-temperature hot springs under the deep sea, and some environments containing extreme chemicals. However, with the development of genome sequencing, especially metagenomic sequencing studies of microbial flora, it has been found that archaea are actually widely present in a variety of environments on Earth, even in our intestines. There is a type of methanogen in the intestines of humans and other mammals such as cows. This archaea helps our digestion and also gives our digestion process some taste.

Archaea that survive in extreme chemical environments often have their own unique way of survival. They have no way to photosynthesize like plants, nor can they obtain nutrients provided by other organisms. Therefore, these archaea have developed ways to obtain energy from chemical reactions. For example, sulfides, which are smelly and toxic to us, can be used as a source of energy. Recent studies by scientists have found that in order to discharge the excess electrons produced in the energy production process, some archaea have evolved a hydrogenase that can catalyze the combination of electrons with hydrogen ions in water to produce hydrogen.

Hydrogenases have been found in bacteria and eukaryotes before, but because archaea live in extreme environments, their hydrogenases can work stably in more extreme environments, which brings hope for the industrial application of hydrogenases. In the future, maybe the hydrogen-powered car you drive will be supplied with hydrogen by archaea.

This article is a work supported by the Science Popularization China Creation Cultivation Program. Author: Ye Sheng

Reviewer: Tao Ning, Associate Researcher, Institute of Biophysics, Chinese Academy of Sciences

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.