Fungus Kingdom

It’s a bit like a plant and a bit like an animal

It turns some animals into “zombies”

It is good and bad for our health

It is closely related to us but ignored

They “shaped” our world today

It may be the future life master of the earth

Huge and unique life circle
Fungus is a unique kingdom of life, a huge and active life circle. Most people think of mushrooms when they hear the word “fungus”, but just as the fruit or flower of a plant is only a part of a plant, and a plant also includes branches and leaves and roots, mushrooms are just the fruiting bodies (organs that produce spores) of certain fungi. Moreover, fungi in the form of mushrooms are only one of the many ways fungi live, and most fungi can release spores without the form of mushrooms.

Fungi have existed for at least 1 billion years. They swallow rocks, make soil, digest pollutants, nourish or kill plants; they can survive in space; they can be used to produce food and make medicines; they can manipulate animals Behaviors affect the composition of the earth’s atmosphere… They are everywhere and omnipotent.

Most people think of mushrooms when they hear the word “fungus”, but mushrooms are just the fruiting bodies (organs that produce spores) of certain fungi.

Fungi use spores to propagate themselves to reproduce their offspring. Fungi on the earth produce as many as 45 million tons of spores each year, equivalent to the mass of 500,000 blue whales. Fungal spores are the largest source of active particles in the air. Scientists even found fungal spores in high-altitude clouds. Fungal spores in the air can affect the weather by forming water droplets and ice crystals.

The spreading ability of fungal spores is extraordinary. Some types of fungi have a strong explosive force when releasing spores, with a release speed of up to 100 kilometers per hour, which is the limit of movement speed that all living things can reach. But releasing spores is not the only way for fungi to expand their reach. In most of the life cycle, most fungi exist in the form of branches and mycelium called “fusion-like cell network” (mycelium is the vegetative body of filamentous fungi, mostly filamentous with multicellular structure) body). The way animals eat is to find and swallow food, and then digest and absorb it, while the way fungi eat is just the opposite-fungi eat by extending mycelium into the food source.

The fungus feeds by extending the mycelium into the food source.

When mycelium passes through the soil, plants and animal bodies (including the bodies of living animals and animal carcasses), water and nutrients flow through the mycelium network. Fungi usually transport and absorb nutrients in this way. Mycelium is everywhere. Mycelium can be found in sediments deep in the ocean, in garbage dumps, and even in old oil paintings hanging in museums. If the mycelium in 1 gram of soil is connected end to end, its length can reach 100 meters to 10 kilometers.

The mycelial network of some fungi is small enough to stick to a grain of dust, and some of the mycelial network is a giant. The largest known fungal hyphae network is in Oregon, USA, weighing hundreds of tons and extending up to 10 kilometers. It is also a rare long-lived species in the world, estimated to be 2,000 to 8,000 years old. There may be many larger and older fungal hyphae webs that have not yet been discovered. The mycelium of some fungal species conducts waves of electrical activity along the hyphae (branching filaments), just like electrical impulses in animal nerve cells.

What is the difference between fungi and bacteria?
Most fungi and bacteria are about the same size, and both are microbes, with the word “bacteria” in their names, but fungi and bacteria are completely different organisms. Although Linnaeus, the founder of modern taxonomy, has doubts about the attribution of fungi, he still classifies fungi together with bacteria and algae (protozoa) as plants. However, fungi and plants are very different: fungi are heterotrophic organisms, while plants are autotrophic organisms; fungi’s cell walls are mainly composed of chitin (a polysaccharide, the main component of crab shells), while plant cell walls are not Contains chitin.

The biggest difference between fungi and bacteria is: fungi are eukaryotes, not only have a nucleus, but also generally have ribosomes, endoplasmic reticulum, lysosomes, vacuoles and other organelles or structures; bacteria have no nucleus, although they have ribosomes, But there are no complete organelles like eukaryotes. Therefore, not only are fungi not closely related to bacteria, but fungi are more closely related to animals (rather than plants).

Symbiosis between fungi and plants
Metabolism is a process of chemical transformation. Fungi can be called the “Wizards” and “Geeks” of metabolism. Their powerful metabolic ability can only be matched by bacteria. Fungi use a mixture of powerful enzymes and acids to break down some of the most stubborn and difficult to decompose substances on the planet. From lignin (the hardest component in wood) to rocks, crude oil, polyurethane plastics and yellow explosives, there is almost nothing that fungi cannot decompose.

There are few extreme environments that prevent fungi from living. For example, a fungus isolated from mining waste is one of the most radiation-resistant species found so far. The ruins of the nuclear reactor after the Chernobyl nuclear accident became a colony of this fungus. Some species of fungi even have a tendency to grow toward radioactive “hot spots” particles, which seem to be able to use radiation as a source of energy.

It is precisely because fungi have such a powerful ability to decompose that we have not seen piles of remains of animals and plants on the earth where we live, so fungi play an indispensable role in maintaining the cleanliness of the earth’s environment.

There are many stories of close cooperation or symbiosis between different organisms in the evolution of life, and fungi are the main participants in the most surprising symbiosis behavior in the history of the earth. About 500 million years ago, plants began to cooperate with fungi to climb ashore from the water and take root on land. Tens of millions of years ago, fungi have been acting as plant roots until plants evolved their own root systems. Today, more than 90% of plants still rely on mycorrhizal fungi. Mycorrhizal fungi obtain essential carbohydrates and other nutrients from plant roots, but at the same time they also provide plant roots with nutrients, enzymes, and water needed for plant growth. The two are mutually beneficial and symbiotic. Mycorrhizal fungi connect trees in the plant root network of “resource sharing”, which is called “tree network”.

To this day, new terrestrial ecosystems are created by fungi. When volcanic islands are formed or glaciers retreat to expose bare rocks, lichens are the first living organisms to appear. Lichens represent the symbiotic relationship between fungi and algae or bacteria. With this symbiotic relationship, there will be soil in which other plants can take root. In a well-developed ecosystem, if there is no tight network formed by fungal tissue to bind the soil together, the soil will be quickly washed away by rain.

For tens of millions of years, fungi have been acting as plant roots. Until the plant has evolved its own root system. The picture shows the mycorrhiza of sunflower.

Fungi are the main players in the most surprising symbiotic behavior in the history of the earth

Mycorrhizal fungi connect trees in a “resource sharing” plant root network.

Lichens in extreme environments
Lichen is a symbiotic organism formed by the combination of fungus and its photosynthetic partner-algae or bacteria. By forming lichens, both fungi and algae can survive in extreme environments.

In some of the hottest and driest deserts, many lichens grow vigorously. Lichen plays a vital ecological role in extreme environments: stabilizing the sand layer on the surface of the desert and reducing the occurrence of sandstorms. In the arid valleys of Antarctica, several kinds of lichens are thriving. In Antarctica, an extreme environment very close to the Martian environment, the powerful lichen ecosystem has achieved great success and withstood unimaginable extreme conditions-long-term cold weather, high-intensity ultraviolet radiation and almost no water. It seems to have no obvious effect on them. Even lichens soaked in liquid nitrogen at -195°C can quickly rejuvenate. The lichen living in Lapland, Sweden, holds the longest life record in the biological world-more than 9,000 years old.

After some lichens are completely dried out under extreme water shortage conditions, they will enter a state of “pseudo-death” where life is suspended. In this state, they can adapt to the space environment full of cosmic rays, so they have become the most concerned in astrobiological research. Life form.

Symbiosis between fungi and animals
Animals also depend on fungi. In addition to humans, the largest and most complex social group on earth is leaf-cutting ants. The largest leaf-cutting ant colony consists of more than 8 million individuals, and their underground nests are more than 30 meters in diameter. The life of leaf-cutting ants is closely related to a fungus. Leaf-cutter ants cultivate fungi in large and deep burrows, feed on the fungi with leaf fragments, and feed on these fungi.

Like most termites, African termites spend most of their lives foraging on wood, but they cannot eat wood directly. Instead, they need to cultivate a fungus called “termite hyphae” to decompose wood. The termites gnaw the wood into wood pulp, and then let the fungi help them decompose the wood pulp in the “fungus garden”, and then feed on the decomposed matter. In order to allow the fungus to “settle down”, the termites will build tall ant mounds as high as 9 meters, some of which have a history of more than 2,000 years. Many of the decomposed forest trees in tropical Africa are food sources for the termite mounds. Like the leaf-cutting ant colony, these large termite colonies belong to a very complex animal group.

The symbiotic relationship between fungi and animals is not always beneficial to all parties involved. Many species of fungi known as “zombie fungi” live in insects, and they change the behavior of the host to suit their own needs. Recently, researchers have discovered that a “zombie fungus” can produce a psychedelic ingredient-psilocybin (an active ingredient produced by hallucinogenic mushrooms), so that they can better “hijack” and “manipulate” cicadas. behavior. There is fossil evidence that the “hijacking” behavior of hallucinogenic mushrooms can be traced back to 48 million years ago, and the behavior has evolved many times.

A fungus that can decompose wood lives in the huge African termite mound.

Disasters and contributions brought by fungi to mankind
There are also many intersections between human society and fungi. Crop diseases caused by fungi can cause huge economic losses. Rice blast destroys more than 60 million people every year. Fungi can also cause many trees to get sick. From Dutch elm disease to chestnut blight, fungi have been affecting forest landscapes and ground landscapes. The impact of fungal diseases is increasing throughout the world: unsustainable farming practices reduce the ability of plants to form beneficial relationships with beneficial fungi on which they depend; widespread use of antifungal chemicals. Leading to the continuous increase of new harmful super fungi. Threatening the health of humans and plants.

Rice blast destroys more than 60 million people every year.

Building materials and textile materials can also be grown from mycelium, and they can replace materials such as plastics and leather in many applications.

At the same time, fungi are also helpful to humans. Humans are already studying how to use fungi to solve a series of pressing problems. In 2017, researchers reconstructed the diet of Neanderthals and found that Neanderthals who had tooth abscesses would eat penicillin, a mold that produces penicillin. This means that Neanderthals may have understood the antibiotic properties of this fungus. In 1928, British scientist Fleming discovered that Penicillium can produce a bactericidal substance, and penicillin became the earliest modern antibiotic.

Because of fungi, we have immunosuppressive drugs-cyclosporine, and organ transplantation becomes possible; only with fungi, we have statins that lower cholesterol… From powerful antiviral and anticancer compounds (including from Paclitaxel, the drug extracted from the fungus living in the yew tree, to the ethanol obtained from the fermentation of yeast, to the drug from the active ingredient of the psychedelic mushroom-psilocybin (it can relieve severe depression and anxiety ), industrial enzymes, vaccines and citric acid in beverages all contribute to fungi.

Fungus has great potential for development
Fungi have great potential yet to be exploited. Advanced technology can help us use fungi to deal with many problems caused by continuous environmental destruction: antiviral compounds produced by fungal mycelium can alleviate the problem of bee colony failure; the huge phagocytic ability of fungi can be used to help decompose pollutants ( For example, crude oil pollution caused by oil spills); mycelium can be used to filter contaminated water (such as removing heavy metals in the water and decomposing toxins); building materials and textile materials can also be grown from the mycelium, and Replace materials such as plastic and leather in many applications. A Swedish company is currently working on a technology to replace polystyrene packaging with fungal substitutes.

However, although fungi play such an important role in human life, people pay much less attention to fungi than to animals and plants. It is estimated that there are 2.2 million to 3.8 million species of fungi in the world. The number of species is 6-10 times that of plant species, but only 6% of them have been described. Our understanding of the diversity and complexity of the fungus world has just begun.

Fungus parasites, ants become “zombies”
In the tropical jungles of Brazil, if you can find a leaf just 25 cm above the ground, you might find a carpenter ant going out foraging on the back of the leaf-its lower jaw is tightly locked to the thickest part of the leaf. The roots and veins, but it has long since died, and the murderer is the terrible hemiplegia, a parasitic fungus that can manipulate the host.

The fungus Snake Cordyceps reproduces through parasitic ants.

Carpenter ants generally live in the upper layer of the tree canopy, and usually only foraging worker ants go out. When they crawl on the woodland, their bodies may be stained with spores of the spores of Cordyceps sinensis. The spores release enzymes to destroy the carpenter ant’s exoskeleton and enter the carpenter ant’s body. When the environmental conditions are right, the spores germinate and grow, which not only consumes the nutrients in the carpenter ants, but also affects the carpenter ants’ behavior.

Two days after being infected with the spores, the carpenter ants will leave the nest in the canopy of the tree alone. It twitches all over during crawling, and it can easily fall from tree trunks and branches to the ground. Next, they will climb to a height where the temperature and humidity are very suitable for the survival of the Snake Cordyceps fungus-generally on a small grass blade 25 cm above the ground, and use the lower jaw to firmly bite the central vein and hang on the blade. Until death. After the carpenter ant dies, the muscles of the lower jaw will shrink rapidly, and the lower jaw will be embedded deeper in the veins, which makes it more difficult for the carpenter ant to fall.

The mycelium of Snake Cordyceps will grow into a long stem, pierce the head of the carpenter ant, extend to the outside, and grow into a globular sac. The globular sac will release new spores below itself and gradually form an infected area of ​​about 1 square meter on the woodland. Once other ants passing through this area are stained with these scattered spores, they will become new hosts for fungi.

How do fungi control ants?
How does hemiplegia and Cordyceps control ants? In order to answer this question, scientists decided to use computer models. They cut the infected ants into many slices each only 50 nanometers thick (only 1/1000 of the diameter of a human hair), scanned them with a computer, built a three-dimensional model of the infected ants, and marked which ants were in the model. Tissues, which are fungal tissues.

Fungal hyphae directly control ant muscles.

Snakes parasitized by fungi.

The three-dimensional model reveals most of the mystery: After entering the body of the ant, the spores of Snake Cordyceps sinensis act independently and move to the chest, abdomen and feet of the infected ant; then, the spores grow out short tubes, which are connected to each other through the short tubes. , And exchange information and nutrients through short tubes, forming a fungal network almost all over the body of the ant; at this time, almost only the exoskeleton of the ant is its own, and the inside has become a world of fungi.

The strange thing is that Hemiphora serrata only surrounds the outer side of the ant’s brain, and does not further invade the brain. Scientists speculate that this may be the fungus in order to allow the ants to crawl to the place where the fungus wants to go alive. Snake Cordyceps can destroy the neurons that control the muscles of the ants, cut off the connection between the ant’s brain and muscles, and at the same time directly control muscle contraction and relaxation by releasing special substances. This is how this fungus controls ants.

Some fungi can even change the behavior of snakes. In 2019, a resident of California, the United States, found a very strange California King Snake near a local highway. Its scales were severely deformed, the eyeballs were cloudy, the head was swollen, and the body was thin. It died shortly after being sent to a wildlife rescue station. Scientists discovered through autopsy that the snake was infected by a fungus. This fungus lives in the soil and can infect snakes through wounds on their bodies. Infected snakes will show abnormal behaviors. For example, snakes that usually like to hide stay in open areas for a long time, and they will take the initiative to go to areas where the temperature is not suitable for their own survival but suitable for fungal reproduction. Scientists speculate that these abnormal behaviors indicate that snakes are being manipulated by fungi.

Offensive and defensive warfare between fungi and plants
Wild plants are constantly under attack from microorganisms such as fungi and bacteria. Take fungi as an example. Their spores will attach to the leaves with the air. The surface of the leaves have stomata that help plants absorb carbon dioxide and discharge oxygen and water. Sometimes, fungal spores can invade the inside of the plant through the stomata, germinate from the inside of the plant and absorb plant nutrients.

But plants have a set of defense strategies specifically against fungi. The cell wall of fungi contains chitin (a polysaccharide), but the cell wall of plants does not. The guard cells located on both sides of the plant stomata can change the degree of opening of the stomata, and can also completely close the stomata. When the fungus attacks the plant, the chitinase in the plant will break down the chitin in the fungal cell into chitin oligosaccharides with shorter molecular chains. Once the guard cells in the plant detect chitin oligosaccharides, they close the stomata and prevent fungal spores from entering.

Fungi invade plant cells.

But fungal spores will not retreat obediently, but will release chitin deacetylase. Under the action of this enzyme, chitin oligosaccharides become chitin oligosaccharides. Chitooligosaccharides will not cause plant guard cells to close the stomata, so fungi can continue to invade plant cells.

Fungus can also infect people
Fungi can also infect people. Athlete’s foot, dandruff and onychomycosis are the most common fungal infections. Approximately 1.7 billion people worldwide are affected by these diseases. Fungi can also invade the mouth and other organs with mucosal tissues. The white thrush in some children’s mouth is caused by a fungal infection called Candida.