[Q & A Collection] 31st National National Institutes of Natural Sciences Symposium-What is alive? ―

1. Where do you think the boundary between matter and living things is? (What is alive?)

Mr. Murata: I wonder if there is a fixed lifespan. The lifespan of an organism is determined by how many cells can divide in that organism. The virus, which is a substance, has no life span because it changes the host cell each time. When asked about cancer cells that grow forever, I think we have to think of them as broken cells for the time being.

Dr. Aoki: At the moment, I think it is between molecules (DNA, proteins, lipids, etc.) and cells. However, the giant virus introduced by Dr. Murata and the extremophiles spoken by Dr. Suzuki are just around this boundary, and the position of the boundary may change as research progresses.

Dr. Tanaka: When living things have the three elements of metabolism, replication, and the boundary with the outside world, the others are considered to be non-living things at this stage. In the dry sleep state of the tardigrade, one of its metabolisms is temporarily stopped, and within this definition, this state is also considered to be a substance. (Tanaka)

Dr. Suzuki: Life works as a cell system, not as a biomolecule. I think that it functions as a self-replicating, self-metabolizing system, and even an evolving system.

2. I am an amateur, I am interested in the origin of life and ask questions. I think that the universe was filled with inorganic substances due to the occurrence of the Big Bang. However, nowadays, both water and humans are filled with organic matter. I don't understand why water was born from inorganic substances and viruses were born. It's as if a monkey was born from a stone. The question is, why did water and viruses come from inorganic substances? Will there be anything that science cannot explain in the tremendous space-time universe?

Dr. Murata: Organic substances can be produced from inorganic substances by chemical synthesis. From this, I think that it is possible in the universe of tremendous time and space. If not, then you will face the more annoying question of where the organic matter came from.

Dr. Aoki: It's just a personal delusion, but I think that the origin of life was a collection of really primitive substances that I don't know if they are living things. It happened to have the ability to self-replicate and evolve, so it evolved over billions of years, resulting in the birth of a wide variety of creatures on Earth today. I am thinking. Therefore, I think it is necessary to consider this evolutionary process when considering living things born from inorganic substances. This is something that is still unsolved in current science, and I think it is very interesting.

Professor Tanaka: There are several hypotheses about the origin of water, the origin of biological substances such as amino acids, and the origin of life, even at this stage. In addition, there is an example of trying to confirm the hypothesis such as "Can organic matter be formed from the composition of the primitive atmosphere (chemical evolution)" like Miller by experiment. By gaining knowledge about the universe and living things including the earth, we will make further hypotheses and verify them. It may not be possible to recreate the earth, but I think science can understand things by testing hypotheses.

Dr. Suzuki: The current knowledge cannot explain it easily. However, it has been confirmed that reactions in various global environments, such as rock-water reactions and meteorite impacts, produce organic matter without life reactions. There is still a distance between life and organic matter, but it is expected that it will gradually become clear as scientific knowledge is collected in the future.

3. Like Margulis's theory of symbiotic evolution, cell-level evolution (change) has occurred many times, and I think it has succeeded or failed (extinct). There is also the truth that no living thing is extinct. It's unscrupulous to say this in a serious situation with a corona wreck, but now isn't it? Some people say that the movie "The Time of Resurrection" is just like an apocalypse that suggests the present. I'm only worried if I live alone with two elderly caregivers. The safety of the virus vaccine and the difficulty and irritation of waiting for treatment are painful.

Dr. Murata: I think that the problem of corona sickness is not a big change in the long-term life of life, because it happened to meet a life form that I had never met before, causing only temporary confusion. ..

Dr. Aoki: Like viruses, humans are also evolving creatures, so I believe that they can overcome or evolve so that they can coexist with this virus. (Aoki)

Professor Tanaka: Living things are constantly exposed to changes in the environment. The environment in this case refers to everything that surrounds us. If it cannot survive for a certain period of time, it cannot survive at least the next generation, and its survival as a species is jeopardized. Therefore, organisms also need to change constantly, and if the changes are adaptive to environmental changes, the chances of survival are high. Since humans are creatures that have a long generation, I think they are one of the creatures that make such adaptations not by genetic changes but by behavior and technology.

Dr. Suzuki: Just as some people are asymptomatically infected, humans have acquired a variety of immune systems through the coexistence of viruses and humans. In addition, humans have succeeded in making vaccines through research and development so far. Therefore, I think we can find a way to overcome Corona!

4. Why does human lifespan never exceed 100 years?

Dr. Murata: The number of times a cell can divide is determined by each organism, and I think that humans will no longer divide in about 100 years.

Dr. Aoki: It seems that researchers have not yet reached a conclusion as to whether or not human life is limited. I have high expectations for future life science research.

Dr. Tanaka: The body of an organism consists of cells, tissues, and organs, and maintenance and repair are performed in various places. It is thought that there are slight errors in this constant function, and the accumulation of these errors leads to the deterioration of the system and eventually causes it to stop functioning. Also at the cellular level there is a limit of the number of times division is known, but in organs and individual level control system and the contact Department I think it worth aging is not the cause. Also, I think that the differences between creatures are related to various factors such as size, temperature, and oxygen consumption.

Dr. Suzuki: It is thought that the number of possible divisions of a cell is predetermined. If we can extend it well, we may be able to overcome it.

5. For those who are deeply researching various fields related to living things, what are your thoughts on the meaning of biodiversity and the significance of existence of each living thing from a bird's-eye view?

Dr. Murata: In a nutshell, the meaning of biodiversity is risk diversification. By diversifying, I think we are preventing the whole thing from becoming extinct at once. I think we must first consider who the significance of existence of living things is. For example, I think that the significance of living things for humankind is that they produce food and decompose waste products.

Dr. Aoki: Biodiversity is essential for living things. In many cases, the loss of diversity makes it impossible to adapt to changes in the environment. This is also the case for diversity within a species. Therefore, it is the same for human beings, and I think it would be good if an environment that maintains, protects, and tolerates diversity for non-human creatures continues.

Professor Tanaka: I think the current biodiversity is the result of evolution adapted to each environment. Furthermore, by coexisting, coexisting, and parasitizing each species with other species, we will build an environment in which we can live and increase the diversity of the environment itself. I think it's a very interesting question whether this diversity is only increasing or if there are any restrictions.

Dr. Suzuki: Just as we live by utilizing the organic matter and oxygen provided by plants, life on the earth coexists in various ways. Diverse life adapts to various places of life and plays a role, and is still evolving and adapting. The creation of diverse lives is the result of the division of roles among those who share the same global environment, and I think that is also the reason for their existence.

6. In a recent pandemic, the Spanish flu 100 years ago killed about 50 million people worldwide, and the world population at that time was 1.9 billion. Today's world population is 7.8 billion, which is exactly the explosive growth of the population, which is one of the triggers for coronavirus infection. We need scientific, peaceful and human solutions.

Dr. Murata: The problem with the coronavirus pandemic is often due to the ease of movement of people around the world. I think that there is no choice but to acquire innate immunity and overcome it with minimal damage by using chemical therapy such as vaccines.

Dr. Aoki: Researchers and healthcare professionals around the world are now confronting the coronavirus. Research on the coronavirus has been promoted at an unprecedented rate in the past year, and the vaccine has been successfully developed. We believe that this pandemic can be overcome by bringing together the wisdom of humankind.

Dr. Tanaka: I think that the probability of getting an infectious disease depends on the population density in a relatively narrow range, but I think that the actual infection depends on the behavioral pattern. I think that social animals such as humans carry the risk of infectious diseases at the cost of benefits such as division of labor.

Dr. Suzuki: There is no doubt that as the population increases, the population density increases, and as a result of the increased movement of humans, the virus infection is more likely to spread than before. I think that various viruses will continue to appear in the future. I think there is no other way but to deal with the problem based on scientific knowledge each time. Even in this battle against the new coronavirus, humankind has a lot of scientific knowledge. I think it will be a great weapon.

7. Which was born first, the virus or the cell? Which is the current mainstream theory? Also, please tell us the grounds.

Dr. Murata: If you think that evolution will progress from simpler to more complex, there is something like the prototype of the virus (nucleic acid mass) first, and this is a kind of external world like oil droplets. I think it is easy to think that it was taken into an environment that is isolated from the virus. (Murata)

Professor Aoki: I'm not a specialist, so I don't know ... But I think the cells are probably the first. Viruses (in the so-called current definition) cannot self-replicate by themselves and must borrow equipment such as self-replication and protein synthesis from some cell. However, we cannot deny the possibility that ancient viruses may have been able to replicate themselves. I think it's an interesting question.

Professor Tanaka: The cells are thought to come first. It's unclear if it's exactly the same as the current cell, but I think the virus will develop later because the virus doesn't have a complete replication system and uses the cell's. I think that is appropriate. In addition, some parasites that promote shrinkage and those that fetch genes from the host are known, and I think that is the difference between general viruses and giant viruses. Therefore, although the virus has a simpler structure than the cell, I think that its development may be after the cell.

Dr. Suzuki: Since the virus alone cannot self-proliferate, it is thought that cells come first.

8. What is the definition of life that is currently mainstream?

Dr. Murata: This hasn't changed from the past, and as I often mentioned in my lectures, (1) being separated from the outside world, (2) metabolizing by myself, and (3) replicating by myself. ,I think.

Dr. Aoki: The current mainstream thinking is (1) self-replication, (2) energy metabolism, and (3) having a boundary with the outside world.

Dr. Tanaka: Many definitions have been proposed, but it is said that the three axes are "distinguishing the region from the outside world by cells", "metabolizing", and "self-renewal". think. Words such as "evolving" and "adapting to the environment" may be added. However, I think that the questions "What are cells in the definition of life?", "What is metabolism?", "What is self-renewal?", And "What is evolution?" I think that the ambiguity of this word is a factor that does not convince each researcher, and is also the reason why researchers must continue to think about this definition in the future.

Dr. Suzuki: I think the basic definitions are that self-replication is possible, that self-metabolism is possible, and that there is a gap with the outside world.

1. What are the types and functions of metals in the active center of viral enzymes?

Viruses also carry genes for many enzymes, and the metal species and functions of each enzyme are diverse and are no different from those of cells.

2. Where is your research motivation?

It's an inspiration that comes from seeing the structure and morphology of viruses that no one has ever seen.

​3. Recent studies suggest that viruses have good and evil implications for humans. So what is the purpose and meaning of life for the virus other than the reproductive instinct?

I think that the greatest meaning of a virus for living organisms is that horizontal gene transfer by the virus accelerates the evolution of living organisms.

4. The story of Professor Murata is very interesting. I support you big and big! Could you tell us the following at the symposium? Did the pithovirus degenerate from the organism? Please tell me the reason why you think. Is there any benefit to the virus as it grows in size?

Pithovirus had a number of features that were not originally found in the virus (not sure if it was necessary for the virus). I think it's easier to think of these as remnants of the bacterial era, rather than as if the virus had acquired its own traits or received them all from the host cell.

5. Is it still unknown whether the virus is the one that jumped out of life or the origin of life? Or is it considered that there is no possibility that the virus was the source of life just because the virus cannot replicate unless it depends on life? Given that evolution has generally been mutated and fused from simple to complex, it seems undeniable that it may have been the source.

Seki of the evolution of the virus and the biological Section is not yet known. As I proposed this time, (1) the idea that a virus has jumped out of life, (2) the idea that a virus was the origin of life, and (3) the idea that a virus is a living thing. There is an idea that it is a fourth domain that does not belong to any of the domains (eunuclear organisms, eubacteria, archaea) (Bluebacks "Giant virus and fourth domain, fourth domain" by Masaharu Takemura). .. I would like to expect new discoveries in science in the future.

6. I have the impression that biomimetics-related research is attracting attention today. What kind of technology do you think it can be applied to through your own research?

There are many possibilities. In a simple place, for example, a giant virus infects and destroys amoeba, so it may be used as a disinfectant for contact lenses. At a higher level, I didn't talk about it this time, but many giant viruses grow by creating their own virus nuclei in host cells called virus factories. Normally, after that, the host cell is destroyed and goes out, but if this state can be maintained, it is possible to completely take over the host cell and turn it into a virus cell. Such things may be applicable to the production of artificial cells.

7. Can the virus leave seeds?

I think there are various viral societies today because viruses leave their species by means of infection.

8. Will the work of the Clio electron microscope not damage cells?

Cryo-electron microscopy is a method that has far less impact on the organism itself than the preparation of biological samples from conventional electron microscopes. Of course, the surface tension of the solution on the verge of quick freezing can physically deform the cells.

9. Will the frozen material not expand?

When irradiated with an electron beam, it expands and bubbling occurs. Record the image before that happens with a cryo-EM. Therefore, the sample after shooting is broken.

10. Isn't a giant virus bad for humans?

At present, there is no such reliable report.

11. Isn't simplification also evolution rather than going against evolution?

That's true. In the talk, when we defined evolution from simpler to more complex, the morphology seen in giant viruses seemed to "go against evolution." For giant viruses, it may be said that they have evolved by scraping off unnecessary things.

12. Doesn't the type of giant virus affect the types of constituent proteins?

Okay. I think that the composition of structural proteins is completely different in pot-type viruses such as pithovirus. This hasn't been revealed yet. On the other hand, in the icosahedron virus that I talked about in the lecture, the shell is basically made by reusing proteins that form equilateral triangles. However, as the shell grows larger, it seems that some reinforcing protein is needed. In addition, it is known that the brick-shaped vaccinia virus uses the protein that forms the equilateral triangle as it is.

13. Did it become huge to take in large base pairs, or did it need large base pairs to make it huge?

It is believed to have become huge in order to take in large base pairs. Many of the genes in giant viruses do not encode the proteins that make up the structure.

14. In the lecture, he explained that living things are generally defined as self-replicating by taking in nutrients, that viruses are not living things, and that Dr. Murata has been studying viruses of particularly large size. I heard. Is it possible that large viruses will be considered organisms in future research? Or do you think that the line between living things and viruses will continue to change and that viruses should be considered non-living forever? I would like to ask Professor Murata's personal opinion.

In my opinion, viruses should be considered non-living, no matter how large they grow. To put it the other way around, smaller creatures may be discovered in the future. Since the definition of living things is "self-replication" and "self-metabolism", it is scientifically meaningful to follow this and discuss why giant viruses and tiny organisms exist. I think.

​15. I would like to know the reason and significance of the simplification that occurred in the evolution of life.

As I wrote in the previous question, giant viruses have a number of characteristics that are not originally found in viruses (I don't know if they are necessary or not). I think it's easier to think of these as remnants of the bacterial era, rather than as if the virus had its own acquired traits or all of them from the host cell. That's why I think simplicity has happened. I don't know what it means unless I ask the giant virus, but I imagine that it means that you can leave offspring without it.

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1. I am interested in physics, and in the fields of cosmology and elementary particles, I am fascinated by the fact that many natural phenomena are explained by the laws of physics (equations). Is it possible to explain life phenomena by the laws of physics? I would like to ask Professor Aoki, who quotes the words of physicist Richard Feynman,. Thank you.

Many life phenomena can be explained by physics. Molecular diffusion phenomena, action potentials of nerve cells, motor molecules (self-driving protein molecules), mechanical properties of cells and tissues, etc. are the subjects of research in the field called biophysics. On the other hand, I think there are still some life phenomena that are still unknown in physics. For example, consciousness or heart. It is expected that a new horizon of physics can be opened by grasping life phenomena as physics.

2. It seems that epigenetics is also the key to molecular genetics, but is there any enzyme involved in phosphorylation other than ERK? Does cell motility also occur with non-ERK phosphorylation?

In addition to ERK, it is known that as many as 500 types of kinases exist in human cells. Cellular movement is a phenomenon in which many molecules cooperate and finally become established. It is known that various kinases other than ERK work there.

3. It was a very ambitious study and was very intriguing. I felt that Professor Aoki's research had a strong sense of deterministic understanding of life. On the other hand, there is thermal fluctuation between molecules and cells, and information processing using this uncertainty can be said to be life-like. What kind of interest does Professor Aoki have in the uncertainty of life?

Thermal fluctuations and uncertainties are very interesting. As you said, there were many deterministic talks at this symposium, but in reality, we focused on stochastic fluctuations (temporal fluctuations) and cell-cell heterogeneity (group fluctuations). I am also doing research. I think that the uncertainty of life is very important and an essential issue for the adaptation strategy of living things.

4. Is AI impossible for cell simulators?

Perhaps in the future, tremendous AI will be born and will create cell simulators without permission, and I know people who are conducting research with such an approach. We think that there is not enough quantitative data to make a cell simulator with high predictive performance, and we are acquiring quantitative data every day.

5. Why is the lizard's ability to regenerate so good?

This may be asked by Dr. Kiyokazu Agata, the Director General of the National Institute for Basic Biology Dr. Agata is studying the regeneration mechanism of planarians, which have higher regeneration ability than lizards. It can be said that the reason why both lizards and planarians have high regenerative ability is that it was advantageous to have high regenerative ability in the process of evolution. Then, when asked why lizards and planarians are superior to other creatures in their ability to regenerate, I think that is still unknown.

1. Can Kumamushi live on the moon?

Survival in the moon, which is said to be free of liquid water and oxygen, may be difficult. Also, since Kumamushi is a heterotrophic organism, the prey organism must be alive as well. From this point as well, it must be said that survival on the moon is difficult.

2. I think that air (oxygen) is indispensable for life in addition to water. What is the resistance of Kumamushi to air? What is the resistance to light (wavelength), sound waves (frequency, amplitude, waveform), radiation, etc.?

Oxygen is essential for aerobic creatures, including tardigrades, but it also oxidizes biological substances. Therefore, when preserving desiccant-tolerant organisms, oxygen may be removed. Regarding electromagnetic waves, while it is resistant to gamma rays and X-rays, it has been reported that irradiation with short wavelength UV (less than 280 nm) in outer space is fatal even in dry-sleeping individuals (Jönsson). et al. 2008).

3. It seems that terrestrial Kumamushi has different drought resistance depending on the species. What is the cause of the difference?

The strength of drought tolerance is defined by whether or not it can withstand rapid desiccation. From the comparison between the tardigrades with strong drought tolerance and the tardigrades with weak drought tolerance, it is considered that the difference in resistance in tardigrades is largely due to the presence or absence of gene expression induction (Yoshida et al. 2017). There may also be differences in the molecular mechanism itself.

4. I used to hit a tardigrade with something like a beam, but does it cause genetic modification in egg cells instead of somatic cells? What happened to the results of the tardigrade protein injection experiment into cultured human cells?

Microinjection is a method of injecting a solution with a glass needle. Currently, we are investigating whether gene editing is possible regardless of cell type. As a result of introducing tardigrade protein into cultured human cells, it was confirmed that hyperosmolar resistance was slightly improved (Tanaka et al. 2015).

5. At the end, I saw the word hyperosmolar stress. Do you know the isotonic fluid of body fluid in Tardigrade? I was curious because I was doing research using Yamakumamushi in high school. I would be happy if you could answer. Thank you.

The following papers describe the ionic composition of multiple species of tardigrades in body fluids.

Inorganic ion composition in Tardigrada: cryptobionts contain a large fraction of unidentified organic solutes,Kenneth Agerlin Halberg, Kristine Wulff Larsen, Aslak Jørgensen, Hans Ramløv, Nadja Møbjerg, Journal of Experimental Biology 2013 216: 1235-1243; doi: 10.1242/jeb.075531

6. Was extremophile acquired after parting in the process of evolution? Or did you lose it because you don't need it?

Some researchers think that organisms basically have the potential for drought resistance because they are resistant to drought across the world and gates, but since the molecules used by each species are not the same, they have evolved to some extent. I think it is reasonable to think that it was acquired multiple times.

7. Is DNA radiation resistant?

Kumamushi DNA itself is thought to be the same as other organisms, but proteins that are thought to protect Kumamushi DNA have been identified (Hashimoto et al. 2016).

8. Have Kumamushi been around for hundreds of millions of years?

A fossil of Kumamushi, presumed to be in the middle of Cambria, seems to have been found, so it is thought that it was around that time (Muller et al. 1995).

9. Is Triops the same?

Like Artemia, Triops (Triops) is resistant to desiccation in dormant eggs.

10. Is the individual recovered from drying the same as the individual before drying?

It is very interesting to see if the memory remains after the revival of dry sleep, but at the moment there is no way to confirm the memory of the tardigrade, and it is unclear.

11. Will the cells not deteriorate?

Individuals who have returned to dry sleep can lay eggs and have almost the same lifespan. However, since the expression of heat shock proteins and the like increases, it does not mean that there is no damage before and after dry sleep, and it seems that the repair mechanism is also used well to overcome it.

1. If there was a designer of the universe, what would life be like in the universe? If you have any opinions through Mr. Suzuki's research, please.

If you are a designer, objectively, I think life is a lot of fun. This is because the reactions are overwhelmingly faster than the geological reactions, and they are evolving steadily. It may be like a pet.

2. Discovery and hearing of microorganisms in the bedrock several kilometers underground. I think it can be said to be a typical example of extremophiles. I was taught what to suggest. I wonder if the perspective that gives special attention to the earth should be abandoned.

We have finally entered an era of advancing life exploration. Many spacecraft are flying in the solar system. In addition, the technological development of telescopes is progressing. It is expected that new knowledge will emerge regarding extraterrestrial life in the future. And if earth-type life exists in other celestial bodies, I think that there may be life like extremophiles living in the similar environment of planets on the earth.

3. CPR? Does the fact that you can't make amino acids mean that you are doing life activities without protein? How is NASA's definition of life, self-preservation, evolution, self-sustaining metabolism and the traditional definition, metabolic self-replication, different from the internal and external boundaries?

CPR cannot make amino acids, but it does make proteins. This means that we are getting various biomolecules including amino acids from other microorganisms. Therefore, it is considered to be a symbiotic life that is highly dependent on others. On the other hand, self-replication and self-preservation are possible. It is also likely that minimal metabolism is possible. Therefore, it is considered that the minimum definition of life is satisfied. It meets the definition, but again, our knowledge of life is often inadequate to explain this life.

4. It is said that genetic defects are found in organisms living in extreme environments. Was that not the case from the beginning? Or is it due to the simplification that Dr. Murata mentioned?

It is thought that many extremophiles have undergone evolution (genome rationalization) in which genes are deleted. This is because the larger the genome size, the higher the cost (energy and nutrition). On the other hand, microorganisms such as CPR, which have a small genome size for the entire family, may have originally had a small genome size. This is currently being analyzed.

<Mr. Murata & Mr. Suzuki>

Giant megaviruses (non-living organisms) with tRNAs with 1000 or more genes were discovered, while park bacteria and OD-1 (organisms) with 400 genes were discovered, both in groups, QS (quarum sensing). ) Is also seen, and is it necessary to review the current biological definitions (metabolism, self-proliferation, membrane) regarding the boundary between living organisms and non-living organisms?

Dr. Murata: I don't think there is any particular need to review the current definition of living organisms for these reasons. What we found from these discoveries is that the boundary between living things and matter cannot be defined by a simple size. On the contrary, I think it is more meaningful as science to discuss why such non-standards exist.

Dr. Suzuki: At this point, I think it is within the range that can be explained by the current definition. You can review the definition at any time. It may be possible to define life more correctly when a little more diverse scientific knowledge of life is gathered.

<Mr. Murata & Mr. Tanaka>

Where do we have the power of will from somewhere else? What is the food for Kumamushi?

Dr. Murata: I think the will comes from a non-living virus. The virus's activities and strategies to infect the host organism and leave offspring may be considered to be the will of the virus.

Professor Tanaka: There are many studies on intelligence and consciousness in other species of animals, but I think it is very difficult to evaluate them. "If a lion could speak, we wouldn't understand it," Wittgenstein wrote (Is human being smart enough to understand the wisdom of animals? Kinokuniya, 2017/8/29, France・ De Waal (Author), Tetsuro Matsuzawa (Supervised), Hiroyuki Shibata (Translated)), I sometimes wonder if the thoughts of each creature can be captured in the same area as humans. And closely related species such as monkeys, Seki, such as the dog Section, but for the resistance of deep creatures might be compared, such as the human behavior patterns, not whether there is thinking about the creatures that live in completely different environments, such as tardigrades I don't think even the current science can reveal it.

It is also believed that carnivorous Kumamushi eats body fluids such as nematodes, and herbivorous Kumamushi eats moss. In the laboratory, we feed and breed green algae called chlorella.