The Human Microbiome

Think for a moment about their vital organs. The heart, brain, lungs, kidneys and liver are complex structures that perform the necessary functions to sustain life. Every moment, day and night, they pump liquids, transfer waste, take air and food, transmit signals that allow us to feel the world and move around it. When any of these organs fail as a result of illness or injury, we die. It's simple.

What if I told you that there is another vital “organ” that sustains life, but which you have never seen? It is on us and within us, and only recently have we realized what an important role it plays in maintaining our health.

Perhaps the most interesting thing is that this part of the body seems completely alien. It does not consist of human cells and is not made according to the drawings of human genes. This trillions of small living beings, microbes and their relatives. You may decide that calling such a meeting a vital organ is too much, but that is what constitutes a microbiome from a functional point of view. Unlike the brain and heart, its development begins not in the womb, but from the moment of birth. In the first few years of life, it continues to develop by getting germs from the people around us. But don’t kid yourself. Losing your entire microbiome at once is almost the same as losing your liver or kidneys. If you don’t live in a suit, you won’t last long.

The microorganisms that live in our bodies are not just a random mixture of all the species that live on Earth. Rather, each creature has evolved with its own set of microbes that perform metabolic and protective functions. In other words, they work for us. There’s a microbiome in a starfish and a shark, there’s even a sponge. Reptiles, every owl, pigeon and hut. When the species survives,so do they. Mammals, from little lemurs to dolphins, from dogs to people, full of microorganisms specialized in the maintenance in them of life and wellbeing.

Microbes-symbionts – provide the host in which they live with vital services in exchange for shelter and food. Termites can digest wood solely because of the bacteria in their intestines. Cows absorb nutrients from the grass they eat thanks to microbes in their four-chamber stomach. Even aphids have them, including Buchnera group, which first settled in them more than 150 million years ago. These microorganisms have key metabolic genes that help to produce proteins – thanks to them aphids can eat sugar-rich plant juice. In turn, bugs are a great home for Buchnera. A win-win situation. Scientists constructed an evolutionary family tree for Buchnera and aphids. Comparing the structure of both trees, we see that they are almost the same. The probability that this is a random coincidence tends to zero. The only possible answer is joint evolution: aphids and bacteria living in them have mutually influenced each other’s development for more than 100 million years.

If you look at the microbiome of mammals, you can see that the genes responsible for the production of red blood cells and proteins in the human body are comparable to similar genes of other mammals. Your bacteria are part of a large family tree. In this sense, the microbial composition can be considered a hereditary marker and helps explain why you are more like monkeys than cows {21}. An interesting question arises: is it due to animals or microbial “genes”? People have always believed that the first option is correct, but it is possible that the second. Most likely, to some extent, both.

As mentioned, your body is an ecosystem, just like a coral reef or a tropical jungle: a complex organization made up of interacting living organisms. And for any of them, diversity is critical. In the jungle, for example, it is all kinds of trees, vines, bushes, flowering plants, ferns, algae, birds, reptiles, amphibians, mammals, insects, fungi and worms. A wide variety protects the inhabitants of the ecosystem because their interaction creates strong networks of capture and circulation of resources. Its loss leads to disease or even to the collapse of the system if the “cornerstone” dies – a species that has a disproportionately large impact on the environment in comparison with the number.

For example, when seventy years ago from the Yellowstone Park and drove the wolves, has experienced explosive growth in the population of elks. Suddenly they were able to eat safely (and eventually completely destroyed) the willows growing on the banks of rivers. The number of songbirds and beavers, which have built of its twigs of the nest and the dam was drastically reduced. River erosion has forced waterfowl to leave the region. Due to the lack of killed wolves fell on the decline went to the population of crows, eagles, forty and bears. The increase in the number of moose led to a decrease in the number of bison due to competition for food. Coyotes returned to the Park and ate mice, which many birds and badgers used to eat. And so on, and so on – the complex network of interactions collapsed when the cornerstone was taken out of it. This concept applies to both the “big” world and your microbiome, where the history of the disappearance of the gastric bacterium Helicobacter pylori, which colonized humans in prehistoric times, should serve as a serious warning.

Your body is made up of about 30 trillion human cells, but it’s also home to another 100 trillion bacterial and fungal cells, friendly microbes that have evolved with our species. Think carefully: they are much more in the body-from 70 to 90%. They live on every inch of skin, in the mouth, in the nose and ears, in the esophagus, stomach and intestines, etc.

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Of the 50 known types of {22} bacteria in humans, 8 to 12 were found. But 99.9 % of the cells in the body belong to six of them, including Bacteroidetes and Firmicutes. The most successful microbes-the winners in the competition for the right to live in humans – come from a very small set of ancestors and form the basis of the human microbiome. Over time, they developed specialized properties that helped them to occupy certain niches of the human body. Among them: the ability to survive in an acidic environment, eat a particular food, prefer dry rather than wet conditions (or Vice versa).

Collectively, these bacteria weigh about one and a half kilograms, about the same weight as your brain, and represent about ten thousand separate species. No zoo in the United States will not have such a variety of animals, as in our invisible human.

While you were in your mother’s womb, you had no bacteria {23}. But during and after childbirth, you were colonized by trillions of microbes. We’ll take a closer look at this amazing process later. Microorganisms multiply very quickly from zero to trillions. In the first three {24} years there is a complex and carefully worked out process of transition from bacteria-“founders” to the subsequent inhabitants.

In the end, each area of the outer and inner surface of the body forms a unique population. Bacteria, fungi, and viruses, such as those on your hands, are not like those in your mouth or intestines.

Your skin is a huge ecosystem just over half the size of a standard sheet of plywood; the area of its planes, folds, wrinkles and crevices is a little less than two square meters. Most of these spaces are very small, even microscopic. Smooth skin, if you look closely, more like the surface of the moon with its craters, hills and valleys. What microbes live where depends on the conditions: whether the oily surface, as on the face, wet as in the armpit, or dry as on the forearm. Sweat glands and hair follicles also have their own germs. Some eat dead skin, others produce moisturizers from oils released by it, others prevent harmful bacteria and fungi from invading your body.

If we talk about the nose, the researchers recently found that many pathogens (pathogens) quite peacefully live in the nasal cavity of healthy people. One of them, Staphylococcus aureus, has a particularly bad reputation. It causes boils, sinusitis, poisoning and even blood poisoning. But it can be quite safe to exist without doing anything. In each time one third, and even more people suffer nose Staphylococcus aureus.

Most microbes live in the digestive tract-from the top, the mouth. Looking in the mirror, you will immediately see that it is divided into several zones – for example, teeth, tongue, cheeks, sky. Each has several surfaces. The tongue has a top and a bottom. Each tooth has several surfaces, plus a place of connection with the gums. We can safely say that each live different bacteria {25}. We learned a lot about this from the human Microbiome project, a five-year programme launched by the National Institute of health in 2007. Among other things, it involved sequencing the genetic material of microbes taken from 250 healthy young people {26}. One of the main conclusions – although the census of the bacterial population and showed considerable similarity between the subjects – each person is unique. At the level of microorganisms, we differ from each other much more than genetic. Our set of microbes is really ours, personal. Nevertheless, there are General principles of the organization. You can consider them on the example of the gastrointestinal tract.

The researchers of the project took a lot of swabs from the mouth. Some families, such as Veillonella, Streptococci and Porphyromonas, were common in many parts of the body, but were distributed differently. Other organisms, on the other hand, inhabited a limited space.

The most rich in microorganisms zone in the mouth – gingival sulcus, the place between the teeth and gums. She is infested, and many anaerobic – do not like oxygen {27}, even die for him. It may seem strange that we have in our mouth, where there is always air, which naturally contains oxygen, live bacteria that are very sensitive to it, but it is so. So there are special niches, including very small ones, where anaerobic bacteria can live and thrive.

Have you ever wondered why the morning breath smells different than the day? That’s because you mostly breathe through your nose when you sleep. Air exchange in the mouth slows down, and the population of anaerobic bacteria grows. They produce chemicals, including volatile, which cause the “morning smell”. Brushing your teeth, you remove food particles and destroy entire populations of bacteria. The total number of is declining, proportion change. This cycle continues throughout the day.

Microbes cause smells not only in the mouth, but wherever they are. In some places, such as in the armpits and groin, the concentration is very high, and in populations dominated by microbes that produce especially odorous substances. Although now whole industries are struggling with this, their presence is not accidental. Starting with insects, microbial smells show who we are: who are friends, who are family, who are enemies,who are loved, who are potential mating partners, and what time is best for this. Mothers know what their children smell like, and Vice versa. Smell is very important, and for the most part create its microbes. He defines even attractiveness for mosquitoes {28}! By understanding exactly how it all works, we can use the information to become invisible or even disgusting to these pests. But I digress.

So, over your food in your mouth worked teeth, saliva, enzymes and friendly bacteria. Next esophagus-a long tube that separates the mouth and throat from the stomach. Until 2004, no one suspected that bacteria lived there-before they found a rich microbial community of dozens of species.

Then the food enters the stomach, where digestion begins with gastric juice and digestive enzymes. Despite the acidic environment, bacteria live there, including the above-mentioned pylori, which, if present, usually dominates. Other species are found in smaller numbers. Your stomach produces hormones like iron – for example, thyroid. The walls contain immune cells that help fight infection like the spleen, lymph nodes or colon. Pylori plays a role in the production of gastric juice and hormones in the immune system.

The next stop – the small intestine, a long tube containing the main elements: detergents, enzymes, conveyors – for decomposition and absorption of food. That's where you digest most of the food. Bacteria there are relatively few-perhaps because excessive microbial activity can interfere with key functions-digestion and absorption of nutrients.

Eventually, what’s left of the food reaches the colon, where bacteria live from wall to wall. There is just the vast majority of microorganisms in your body. The numbers are amazing. In one milliliter of the contents of the colon (and its volume – a few thousand) more than people on Earth. This is a whole universe of microorganisms, tightly Packed, chemically active, accompanying you during your life. This situation may seem like an inevitable deal: we give them food and shelter, and they support us for it. But this simplification is not entirely true. Thousands of people lost their colon and all the bacteria it contained due to disease or injury, but many then lived a few decades quite healthy. So while this ocean of bacteria is very useful, it is not vital. (Again, this is not the case for the entire microbiome; its total loss is likely to be catastrophic.)

Microbes in the large intestine decompose the fiber and digest the starch. In a sense, everything that has reached the end of your small intestine will be expelled from the body, because you could not digest it. Hungry bacteria learn a lot of things, digest and turn into food – mostly to feed themselves. But some substances produced by them, in particular molecules called short-chain fatty acids, still go into our food-starting with the cells of the colon wall. Feed the owner of his “hotel”.

Up to 15% of the calories from food are processed in the colon and used to feed you. Like all microbes, its inhabitants are not just random guests – we have evolved to help each other. All mammals, even those whose last common ancestors lived tens of millions of years ago, have a marked similarity between the types of intestinal bacteria and their functions.

It is warm and humid; there are several “districts” inhabited by specialized microorganisms. Those that produce specific vitamins can be located on small heels, but those that process starch into simple sugars live in a larger area. There is competition. As in cities: good Parking and places in prestigious schools are not easy to get. Bacteria, feeding on the same substances, armed with the same enzymes and, like lions and cheetahs, hunting for the same prey, fiercely compete with each other. It seems to me that many of them want to get into the same soft layers of mucus and use the same few shelters, protected from severe rains of gastric juice or bile. At the same time, the cells that cover the gastrointestinal tract are dumped every day, so that today’s shelter can tomorrow turn into a sinking ship. After all, when the remnants of digested food leave your body as feces, a mixture of bacterial cells as well as old intestinal wall cells come out with them. Together they, their fragments and water make up the main part of your chair.

To understand how important microorganisms play in metabolism, think about this: almost all chemical substances in the blood are the result of microbial activity. In addition, bacteria digest lactose, produce amino acids and decompose fibers in strawberries or, for example, if you eat sushi, in algae.

With the help of substances produced by them, it is possible to maintain stable blood pressure – thanks to special receptors in the blood cells (and, oddly enough, in the nose). These sensors detect small molecules created by microbes that inhabit the intestines. The reaction to them affects the pressure. Thus, after a meal it is usually lowered. Will we ever be able to get a cure for hypertension where these bacteria are used? Quite probable.

The microbes process the medication. For example, millions of people around the world take digoxin – a substance extracted from digitalis, for the treatment of various heart diseases. How much it specifically gets into the blood depends on the composition of the human microbiome; the first chemical treatment and assimilation {32} occur in the intestine. Chemical differences have consequences. If the dose is too low, the drug won’t work. If, on the contrary, too high, the patient may get additional heart problems, changes in color perception and indigestion. In the future, doctors may be able to control this process by activating or inhibiting intestinal microbes.

Some bacteria produce vitamin K, which is necessary for blood clotting, which is not done by the body’s own cells. It is possible to rely on bacteria for its production turned out to be more effective for the human body than to go to additional metabolic difficulties, that is, to produce independently. So our ancestors won the competition counterparts, which had either by making him work, or gather from plants. In a sense, we can say that ancestors outsourced the key metabolic function. We fed them and sheltered them, and they help to curdle blood – a wonderful exchange.

Some produce endogenous “valium“. The people who are dying from cancer of the liver, often inducing a coma. But if you give them a substance that inhibits benzodiazepines (which include “valium”), they Wake up. The fact that a healthy liver decomposes natural benzodiazepines produced by intestinal microbes, but the diseased liver-no, so that “home valium” comes directly to the brain and lulls the patient. Other microbes allow the mountain peoples of New Guinea to live on a diet of 90% of which is sweet potatoes, in which little protein {33}. Like bacteria living on the roots of legumes, the intestinal microbes of these tribes produce it from atmospheric nitrogen in the intestines of the hosts and create amino acids.

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In women, bacteria colonize and protect the vagina. Until recently, doctors believed that only one group of bacteria, lactobacilli, protects against pathogens, for example, pathogens of thrush. Indeed, they produce lactic acid, which reduces the acid-base balance, making the environment acidic and less hospitable to pathogens. Women with other bacteria living in their vaginas were thought to be more vulnerable to vaginal diseases. But now that microbial DNA sequences from hundreds of healthy women are available, we know that there are five main types of vaginal microbiota, only four of which are dominated by lactobacilli. In the fifth lactobacilli, in fact, no {34}. In women with this type live codominant a few other species. But, contrary to popular belief, it does not increase the likelihood of developing vaginal diseases, and its owners do not belong to a small minority. Such “abnormal” mixture has about a third of all women.

In women without lactobacilli, the acid-base balance of the vagina is slightly higher, but their bacteria are able to create an unfriendly environment for uninvited guests no less effectively. Similar functional substitutions are likely to occur throughout the body; different people have the same job done by different bacteria.

In addition, we learned that the population in the vagina changes over time. For example, during the most part of the month the bacterium dominates, and during the month the other one is experiencing a decline, and after that the bacterium quickly goes down. Everything seems to be clear, but such a schedule is rather an exception. The most common scheme – the absence of any scheme. Sometimes the dominant bacteria change in the middle of the menstrual cycle, and the next month-at the end of the cycle. Sometimes nothing changes at all. Periodically, lactobacilli begin to dominate in turn, as if playing leapfrog. In some cases, “unusual” bacteria predominate, which then disappear without any apparent reason. We still have not solved the mystery of these unexpected and significant changes.

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Perhaps the most important service that bacteria provide to us is immunity.

Microbes are an important third branch of the immune system. The first is innate immunity. It is based on the fact that most of the micro-organisms with which we are in contact, there are similar structural features that “see” proteins and cells that protect our surfaces. The second is adaptive immunity, the ability to recognize specific chemical structures. The basis of microbial immunity-bacteria that already live in your body, long-term inhabitants, do not let newcomers, using a variety of mechanisms. We’ll take a closer look at all these branches.

The interaction between the immune system and microbes begins at birth and lasts a lifetime. It’s logical. One of the essential properties of your inhabitants – hostility to uninvited guests. In fact, the friendly microbes happy and the place of residence, and life itself. They’re not happy about aliens. For example, when someone from the outside tries to gain a foothold in your gut, they first need to pass the barrier in the form of gastric juice, which kills most bacteria. It is produced by humans, but the production itself stimulates the bacteria living there, for example. If the alien still manages to get to the intestine, you need to find a source of food and a place to settle. But there is already crowded. Your bacteria are not eager to share the reclaimed place on the intestinal wall. And perishing to share food-and all the. So they secrete substances, including their own antibiotics, poisonous to other bacteria.

Some alien microbes manage to gain a foothold for a few days, after which they die – in fact, most often it happens that way. The fact is that your microbes maintain a fairly stable situation. When you kiss someone, you exchange a lot of microorganisms. But soon-in a few minutes, hours, maximum days – both you and your partner will return to the former microbial composition. There are, of course, exceptions: you can get from a partner harmful pathogens. But usually the ability to resist invasion, even from a rather attractive person with whom you wanted to kiss, is very high. The same can be said about sexual intercourse. There is an exchange not only liquids, but also microbes, and something is changing in both carriers. But soon you and your partner return to their previous state, as if nothing (from a microbial point of view) has happened. Some may migrate regularly between sexual partners, but we do not yet have data on them – with the exception of pathogens, which often have a well-developed method of distribution between individual carriers.

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Even a change in diet is not too effective on microbes. In the long term (months, years), the composition of the human intestinal microbiome does not change too much, but your microbiome is different from mine. In one small study, people sat on a Mediterranean diet for two weeks: lots of fibrous food, whole grains, dry beans and lentils, olive oil, five servings of fruit and vegetables each day. It is associated with a reduced risk of cardiovascular disease. Everyone donated blood to lipids correlating with heart disease and stool samples to determine how the microbial composition of the intestine changed after the diet. The researchers found a decrease in total cholesterol, as well as so – called “bad” cholesterol, or LDL, is just wonderful. But the microbial composition after the diet has not changed in any way.

Each person has their own unique microbial “signature”, like fingerprints. And it remained the same even after manipulating the diet. However, in other studies, changes in the microbial population were more significant {36}. For example, eating only plant or animal food affected the microbiota, but only while people were on this diet {37}. We don’t know how long it takes before the changes become permanent – maybe a year. There’s still a lot of research to be done to understand how the diet affects intestinal microbes. But at the moment it seems that the relative proportions of different bacteria change only within certain limits. Now researchers are trying to find out whether they are the same in different people and how much change during life.

If you have 100 trillion bacteria living in you, and each is a small genetic machine, how many genes do your microbes have and what do they do?

As we have already discussed, one of the goals of the project “human Microbiome” was the sequencing of the genetic material of microbes taken from the body of young healthy people. Scientists not only conducted a census, which listed the microbes living in organisms (“who’s there”), but also made a list of genes that carried these microorganisms, and described their functions (“what’s there”). The main discovery is that your or my microbes have millions of unique genes {38}; according to the latest data, there are about 2 million of them, compared to 23,000 genes in the human genome. In other words, 99% of the unique genes in your body are bacterial, and only 1% are human. Our microbes are not just passengers, but active participants of metabolism. Their genes encode foods that are good for them. Enzymes produce ammonia or vinegar, carbon dioxide, methane or hydrogen, which are consumed by other microbes. As well as many other, much more complex substances, useful for the body – we are still trying to understand how it happens.

A recent survey conducted by a large group of scientists in Europe (it started at the MetaHit consortium) showed something quite different. The census of almost three hundred Europeans showed that the number of unique bacterial genes in the intestines of the subjects differed sharply. The distribution turned out to be abnormal, in the form of a bell-shaped curve. Instead, two separate groups were found. In a large, which included 77 % of the participants, found an average of 800,000 genes. The smaller-23 % – only 40 000. No one expected such a difference. But the most interesting observation was that people with fewer genes were more likely to be obese. This is an amazing result.

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The study of the ecological structure of bacteria-inhabitants-a very complex procedure. In a large ecosystem, such as a forest, ecologists can directly observe different individuals and species interacting in real time throughout the day, season or year. But it will not be possible to study microbial ecosystems in this way. As mentioned above, one of the best modern methods is to count and identify all genes in a particular community. Let’s think of it this way. We’ll take an entire acre of forest, run it through a giant blender, and then count the remaining fragments of leaves, wood, bones, roots, feathers and claws; from these remains, debris and scraps, we’ll make a rough list of the inhabitants and assume how they interact.

We can understand the function of some bacterial genes by comparing them with other known ones. The first data of the project “human Microbiome” and the European program MetaHit basically gave us the so-called” genes of home Economics”: they are engaged in routine, but necessary for life work. For example, genes are abundant for building and maintaining a cell wall, because all bacteria are required to build them. In addition, everyone should have genes that allow them to reproduce their own DNA and reproduce. Genes for the key enzyme, DNA polymerase, necessary for the creation of new chains were also found. People have several variants of it, the microbes living in us must be thousands, depending on what kind of bacteria it contains.

In the genes of bacteria found in different parts of the body, there are less subtle differences. “Genes of home Economics”, of course, remain constant, but for example, skin bacteria have more of those that are associated with oils than the inhabitants of the colon. Have vaginal have genes that help create an acidic environment and survive in it. Based on today’s level of knowledge, we can safely say that microorganisms perform specialized functions in all inhabited areas of the body, and the difference between them can be much greater than between people. For example, the tallest man on Earth is twice as tall as the lowest man on earth, three times as high. The difference in the size of organisms of a typical microbiome can be a striking ten million units. Bacterial specialization is a very interesting and largely unexplored world that will help you understand what makes each of us unique in terms of health, metabolism, immunity and even cognitive abilities.

We have not yet determined the function of 30-40% of bacterial genes found in large-scale projects, but we know that some species are rare and may be threatened with extinction. The microbial population as a whole is very dynamic. The number of cells representing a particular species can range from one to a trillion. Let’s assume that the animal has found a new food, which contains an unfamiliar chemical substance {41}. The type of bacteria, whose population was only a hundred cells, is able to reproduce in a few days to billions as a result of changes in the intestinal environment due to new food. If previously the dominant species will not withstand competition for food with a new hungry bacteria, its number may be reduced by several thousand times, or even more. It is dynamism and flexibility that are the main characteristics of the microbiome that help it thrive. But on the other hand, a species that is normally represented by only a hundred cells, there is no room for error. He may encounter an antibiotic that will completely destroy him.

I call these rare species ” microbes just in case.” Not only can they exploit an unusual food substance (the more common ones generally cannot), but they can also, say, provide genetic protection against threats, such as a disease that people have not yet had to deal with. For me it is a bright alarm. Diversity is vital. What if we lose critically important rare species? What if the cornerstones of the human microbial ecosystem were to disappear? Will it lead to the extinction of other species on the principle of dominoes?

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Our coexistence with bacteria forces us to ask many important questions. Why didn’t they destroy us? Why do we tolerate them? How in the ruthless world of Darwinian competition was it possible to achieve stable relations with our microorganisms?

The answers to these questions can give the theory of public goods-this is what is available to all: for example, clean air, which you breathe on the beach, bright Sunny day, a new street, built including your taxes, favorite public radio station. But nothing is really free. Public radio should be supported, respectively, someone has to pay for it. Clean air is a public good, but your car emits substances that pollute my clean air. I breathe in the same space you drive in.

In a well-functioning social world, every individual is expected to contribute to the public good. You can listen to public radio and not pay the bill, but if everyone does, the radio station will go bankrupt. If everyone has cars with” dirty ” engines, the General air and sunlight will suffer. From this point of view, people who use the public good, but do not give enough in return, can be called “scammers”: they benefit, but do not pay for it.

However, in a jungle ruled by the law of survival of the fittest, “fraud” seems like a pretty good strategy. A bird-cheater can, for example, lay more eggs or find a better place for nesting and for several generations achieve considerable success (leave more offspring), because the benefits of such behavior exceed the costs. They have an advantage in the selection. However, if the “scammers” always won, no cooperation would be observed. Why doesn’t everyone become a Freeloader and refuse to Fund public radio? How can different living creatures live together if the advantage in the selection is owned by those who break the rules? Fraud can easily destroy the entire system.

Nevertheless, wherever we look, we see cooperation: bees and flowers, sharks and pilot fish, cows and rumen bacteria that help them extract energy from grass, termites and aphids. As far as we know, ruminants exist for millions of years, and insects, the same aphids and termites, and even longer. This means that scammers don’t always win. Simply put, the punishment for this must be so high that the process becomes unprofitable. If there were no consequences, most people would be speeding on the roads. Punishments are effective.

The same principle applies to microbes. Natural selection encourages carriers with a system of penalties that cannot be avoided: the greater the fraud, the stronger it is. You can spoil prey, “acquired by dishonest means”. For example, the bacteria in the intestine of the termite, which is beyond clearly marked boundaries, facing the strongest immune response, which puts her in her place. It works, but for a carrier, such a system can be a very expensive luxury. Some die, when the immune system is overly aggressive fighting scams. Dies and the carrier die and all its inhabitants. When this happens, the genes – of both the host and the inhabitants – are forever lost to the offspring. There are other termites in which there are no scammers, and occupy an ecological niche left by a recently deceased brother. The confrontation between competition and cooperation is played out simultaneously on a thousand “scenes”.

Game theory, created by the great economist and mathematician John Nash (whose biography is known to us from the book and film mind Games), sheds light on the phenomenon of collaboration, on the question of why selection in co-evolving systems encourages individuals who play mostly by the rules. It also helps to understand societal behavior: how people make decisions to optimize outcomes and how markets work. Nash presented the situation which now became known as the “Nash equilibrium”. In short, it is a strategy in a game with two or more players, where the result is optimal if you play by the rules; if you cheat, it will be worse.

Ecosystems that have been around for a long time, like our bodies, have managed to resolve a fundamental conflict between competition and cooperation. We survived. But this theory is still important-at least look at our changing world. Cooperation is a very weak thing: if you break it, then anything is possible. I’m afraid that because of the excessive use of antibiotics, as well as some other common practices, such as caesarean section, we have entered a danger zone, a no man’s land between the ancient microbiome and the modern world, the map of which still does not exist.

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