Are ancestors of "eukaryotes" including animals such as humans?

Is ancestor of "eukaryotes" including animals such as humans? Successful culture of microorganisms.

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We have succeeded in culturing microorganisms that are likely to be ancestors of a group called eukaryotic organisms including animals such as humans, and research groups such as the Japan Agency for Marine-Earth Science and Technology announced that the evolution of organisms Has been attracting attention as a major achievement that unravels one of the mysteries in.

`` Eukaryotes '' are characterized by having organs such as nuclei and mitochondria in cells, and animals and plants such as humans are also included in this, and about 2 billion years ago a microorganism could It is thought that it was born from the incorporation, but we did not know in detail what kind of microorganism it was based on.

Under such circumstances, a research group such as Hiroyuki Imachi, Senior Research Fellow of the Japan Agency for Marine-Earth Science and Technology, uses special equipment to culture microorganisms likely to be ancestral eukaryotes from mud collected in the deep sea off the Kii Peninsula. Succeeded.

While this organism exhibited primitive microbial features, such as the absence of cell nuclei, it had over 80 metabolic and motility genes that only eukaryotes have.

Although this microorganism is in the form of a sphere, it has also been found that as culture continues, long protrusions like tentacles are formed, and the research group may use this protrusion to take up another microorganism into cells. It is considered possible.

Also, it took about two to three weeks for this microorganism to split into two, and the growth speed was extremely slow. This research was selected as one of the last 10 major news published last month by the famous science magazine "Science" in the United States, and was highly evaluated as a major achievement in solving one of the mysteries in the evolution of living things.

Dr. Hiroyuki Imachi said, "We have been able to culture for 12 years and have achieved great results. We would like to investigate the detailed ecology of this microorganism and further explore the mystery of the evolution of living organisms." .

What is "eukaryote"?

Eukaryotes are characterized by having small organs such as nuclei, mitochondria, and chloroplasts in which DNA is enveloped in cells.

It is thought that microorganisms evolved about two billion years ago when they took in other microorganisms, which enabled them to increase their metabolism and grow faster.

By creating multicellular organisms and evolving into organisms with complex structures such as organs and nervous systems, we have created large and diverse organisms such as humans and other animals and plants.

Until now, it has been estimated what kind of microorganisms turned into mitochondria and chloroplasts by incorporation, but it is not clear in detail what kind of microorganism was the ingesting side Has long been a mystery of evolution.

This result can be said to have identified microorganisms that seem to be the ancestors of each and every cell that makes up our body. To solve this evolutionary mystery, researchers have been studying the phenomenon in which one microorganism takes up another microorganism.

This is because it has been known that certain microorganisms take in other algae, keep them alive, make nutrients, and use them.

This is thought to be similar to the process by which chloroplasts are formed, but they cannot keep alive and microorganisms dissolve and absorb the algae within a few days and try to take up the algae again.

What evolved into a eukaryote is what has evolved so that microorganisms can keep alive.

What microorganisms have been successfully cultured?

The microorganism that was successfully cultured was a microorganism called archaea that was collected from mud on the seabed at a depth of about 2500 meters off the Kii Peninsula.

This kind of microorganisms has been found to be distributed on the sea floor and underground, but most of them could not be cultured, so detailed properties could not be studied.

This time, the research group applied a method of treating sewage, developed a special method to increase microorganisms over time in a sponge without touching the air, and succeeded in culturing. I was able to name it.

It took 12 years to be able to cultivate the cells, and when examining the genes of this microorganism, it was found that eukaryotic organisms have unique genes, such as genes involved in the formation of cell nuclei and genes that maintain intracellular structures. It turns out that there are about 80 genes that have been considered to be.

In addition, it has a characteristic shape, which is spherical in the early stage of culture, but when culture is continued as it is, the shape changes drastically, showing an unusual shape in which multiple long tentacle-like projections are formed.

The group named the microorganism Prometheaaeca, named after Prometheus, a Greek mythological god who made humans out of the mud.

This means that there is a possibility that this microorganism can take up another microorganism efficiently by using characteristic protrusions.

The results of this research were selected as one of the 10 major news articles published last month by a famous American scientific journal, "Science," and were praised as a major achievement that unraveled one of the mysteries in the evolution of living things.

Experts have pointed out that further discoveries to elucidate the mysteries of life are expected to continue, and that research on culturing microorganisms on the seabed and underground that cannot be cultured at present will be active.