Does not provide spore formation in bacteria. Spore formation in bacteria. Ecological groups of fungi

bacterial spore formation

Some types of rod-shaped bacteria (genus Bacillus and genus Clostridium) are able to form spores. Sporulation is induced by unfavorable environmental conditions (changes in temperature, lack of nutrients, accumulation of toxic metabolic products, changes in pH, decrease in moisture content, etc.). Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, sporulation is not an obligatory stage in the development of spore-forming bacteria.

Only one spore is always formed in a cell.

The main stages of spore formation are:

1. Preparatory stage. The process is preceded by a restructuring of the genetic apparatus of the cell: nuclear DNA is pulled out in the form of a thread and concentrated at one of the poles of the cell or in the center, depending on the type of bacteria. This part of the cell is called sporogenic zone.

2. Prospore formation. In the sporogenous zone, dehydration and compaction of the cytoplasm and the isolation of this zone with the help of a septum formed from the cytoplasmic membrane occur.

Prospora - a structure located inside the cell and separated from it by two membranes.

3. Formation of spore envelopes. A cortical layer (cortex) is formed between the membranes, similar in composition to the cell wall of a vegetative cell. In addition to peptidoglycan - murein, the cortex contains a calcium salt dipicoline acid, which is synthesized by the cell in the process of sporulation. Further, a spore envelope is synthesized on top of the membrane, consisting of several layers. The number and structure of the layers are different in different types of bacteria. The shell is impermeable to water and solutes and provides greater resistance of spores to external influences.

4. Release of the spore from the cell. After maturation of the spore, the shell is destroyed, and the spore comes out.

The process of sporulation lasts several hours.

Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, dispute - This is a dehydrated cell covered with a multilayer membrane, which includes the calcium salt of dipicolinic acid. The main feature of bacterial spores is their high thermal stability.

Once in favorable conditions, the dispute germinates. The process of transformation of a spore into a growing (vegetative) cell begins with the absorption of water and swelling. At the same time, profound physiological changes occur: breathing intensifies and enzymes are activated. In the same period, the dispute loses its thermal stability. Further, its outer shell is torn, and a vegetative cell is formed from the resulting structure.

Spore formation of bacteria - concept and types. Classification and features of the category "Spore formation of bacteria" 2017, 2018.

Bacteria in the process of evolution adapted to survive in the most adverse environmental conditions and retained hereditary information through the formation of spores. Bacterial spores form inside the cell. The whole process of germination (sporulation) lasts 18 - 20 hours. During this process, a number of biochemical processes change in the bacterial cell. Bacteria can remain in a spore-like state for a long time - hundreds of years. Under favorable environmental conditions, spores germinate. The germination process lasts 4-5 hours.

Sporulation occurs when:

• the nutrient substrate is depleted,
• there is a lack of carbon and nitrogen,
• accumulates in the internal environment of the cell potassium and manganese ions,
• the level of acidity of the environment changes, etc.

Rice. 1. In the photo of a spore inside a bacterial cell (the photo was taken in the light of an electron microscope - EM).

Which bacteria are capable of sporulation

Rod-shaped bacteria that form spores are called bacilli. They belong to the family Bacillaceae and are represented by the Clostridium genus Clostricdium, the Bacillus genus, and the Desulfotomaculum genus. They are all gram positive anaerobic bacteria.

Genus Clostridium contains more than 93 types of bacteria. All of them form disputes. Clostridium species cause pulmonary gangrene, are the culprits of complications after abortion and childbirth, severe toxic infections, including botulism. Spores of bacteria of this species exceed the diameter of the vegetative cell.

Genus bacillus has more than 217 species of bacteria. Pathogenic bacteria of the genus Bacillus cause a number of diseases in humans and animals, including food poisoning and anthrax. Spores of bacteria of this species do not exceed the diameter of the vegetative cell.

Rice. 2. In the photo, bacteria of the genus Clostridium. Left: Clostridia perfingens. They are the causative agents of food poisoning and gas gangrene. Right: Clostridium botulinum. Bacteria cause severe food poisoning - botulism.

Rice. 3. In the photo, the causative agent of anthrax. Bacillus anthracis genus Bacillus is a large, immobile, stub-ended bacterium (left) and a spore-like bacterium (right).

Sporulation in bacteria

Preparatory stage

Before the formation of the spore itself in the vegetative bacterial cell, the level of metabolism decreases, DNA replication stops, one of the nucleotides is localized in the sporogenous zone, and dipicolinic acid begins to be synthesized.

Formation of the sporogenous zone

The formation of the sporogenous zone begins with the compaction of the cytoplasmic region in which the nucleotide is located ( prospore). The isolation of the sporogenous zone occurs with the help of the cytoplasmic membrane, which begins to grow inside the cell.

Prospore and spore formation

A cortex is formed between the inner and outer layers of the membrane. One of its components is dipicolinic acid, which determines the heat resistance of the spore.

The side of the membrane facing outward is covered with a shell (exospore). It consists of proteins, lipids and other compounds that are not found in a vegetative cell. The shell is thick and loose. Possesses hydrophobicity.

Spore maturation

During the period of spore maturation, the formation of all its structures ends. The spore becomes heat resistant. It takes a certain form and occupies a special position in the cell. After full maturation of the spore, autolysis of the cell occurs.

Rice. 4. The photo shows the formed spore, along the periphery of which there are remnants of the cytoplasm.

Rice. 5. The photo on the left shows a newly formed spore (A), along the periphery of which there are remnants of the cytoplasm. The cytoplasm then dies. In the photo on the right (B) is a spore purified in the laboratory.

Rice. 6. In the photo above, the stage of sporulation is from the formation of the sporogenous zone to the complete formation and lysis of cell residues. In the photo below, a dispute with ribbon-like outgrowths. O is its outer shell, K is the cortex, C is the inner part.

cortex

The cortex protects the spore from enzymes that are produced in large quantities by the cell at the final stage of sporulation. Their purpose is to completely destroy the maternal vegetative cell. In the absence of a cortex, bacterial spores are lysed. Cortex contains diaminopimelic acid, which provides thermal stability

The inner side of the cortex is adjacent to the inner side of the cytoplasmic membrane. During spore germination, the cortex transforms into the cell wall of the vegetative cell.

Spore shell (exosporium)

The side of the cytoplasmic membrane, facing outward, is covered with a shell (exospore) during spore formation. It consists of proteins, lipids and other compounds that are not found in a vegetative cell. The shell is thick and loose. It makes up about 50% of the volume of the spore itself. Possesses hydrophobicity. The outer wall of the spore is resistant to enzymes. It prevents the spore from premature germination.

Rice. 7. In the photo of a dispute with outgrowths. Its core is a resting vegetative cell.

Outgrowths on spores

On some spores, outgrowths are formed in the process of spore formation. They are varied and specific. This feature for each bacterium is hereditarily fixed and constant. Outgrowths on spores consist mainly of protein. The amino acids of the protein are similar to those of keratin and collagen. The function of outgrowths on spores has not yet been finally elucidated.

Rice. 8. Types of outgrowths on spores: flagella, tubes, ruff-shaped sticks, wide ribbons, spikes, pins, in the form of deer antlers.

Rice. 9. In the photo, spores of bacteria of the genus Clostridium. Outgrowths in the form of tubes (1 and 5), outgrowths in the form of flagella (2), ribbon-like outgrowths (3), pinnate outgrowths (4), spores, on the surface of which there are spikes (6).

Characterization of bacterial spores

In a cell that is in a spore-like state, it is noted:

• complete repression of the genome,
• almost complete lack of metabolism,
• a decrease in the amount of water in the cytoplasm by 50% (a significant loss of water by the cell leads to its death),
• increased amount of calcium and magnesium cations in the cytoplasm,
• the appearance of dipicolinic acid and cortex responsible for thermal stability,
• increase in the amount of cysteine ​​​​protein and hydrophobic amino acids,
• remains viable for hundreds of years.

Spore persistence

In the process of spore formation, the spore is covered with shells - the outer shell and the cortex. They protect the spore from adverse environmental conditions.

cortex contains diaminopimelic acid, which is responsible for thermal stability. Outer shell protects the spore from premature germination and negative environmental factors.

In the spore-like state, the bacterium is resistant to elevated ambient temperatures and drying. It is able to survive in solutions with a high salt content, endure prolonged boiling and freezing, radiation and vacuum, and ultraviolet irradiation. The spore is resistant to a range of toxic substances and disinfectants.

The stability of spores of pathogenic bacteria in the external environment contributes to the persistence of infection and the development of severe infectious diseases.

Type, shape and location of spores in bacteria

Bacterial spores are oval and spherical in shape. They can be located at the ends of the cell (causative agents of tetanus), closer to the center (causative agents of botulism and gas gangrene), or in the central part of the cell (anthrax bacillus). Less commonly, bacterial spores are located laterally.

Rice. 10. The photo shows terminal endospores of C. difficile and Clostridium tetani.

Rice. 11. The photo shows centrally located spores of Bacillus cereus bacteria.

Rice. 12. In the photo, the terminal location of the spore in the bacterium Bacillus subtilis.

Spore caps

On spores of the genus Clostridium and Bacillus, caps are formed in the process of spore formation. They have a conical or crescent shape and a cellular structure. The cells resemble sacs that are filled with a gaseous substance. They are in the form of sticks or ovals. The cells help the spore stay buoyant in the water. Even with centrifugation, capped spores cannot be settled. Caps on spores are formed in soil bacteria of hydromorphic soils that have formed under conditions of stagnant surface water or in the presence of groundwater.

Rice. 13. In the photo, caps on spores are cone-shaped (left) and crescent-shaped (right).

Rice. 14. In the photo, the structure of the bacterial spore cap. Individual gas cells (vacuoles, sacs) of an oval shape are visible.

Some rod-shaped bacteria, once in unfavorable conditions, form round or elliptical bodies inside their cells, called spores. Almost the entire content of the protoplasm is spent on their formation. First formed prospore , which then turns into a spore. The process of spore formation takes from 40-50 minutes. up to several hours, and sometimes it drags on for a whole day. Spore-bearing cells lose their ability to reproduce. After maturation of the spore, the remnants of the vegetative cell die and are destroyed. Outer shell - exine becomes impermeable to water and substances dissolved in it. Inner shell - intina plays an important role in spore germination. A shell for a new vegetative cell is built from it. The water in the spore is in a special state, the enzymes are inactive, the shell limits the exchange of spores with the external environment - all this allows the spores to remain in a viable state for tens and hundreds of years. Hence, spore is a resistant form of bacteria to adverse environmental conditions . For example, when river water is boiled, all bacterial cells die, except for spore-forming ones. Spores do not die when dried, frozen, exposed to direct sunlight and strong chemical poisons. Spores die when they are sterilized in autoclaves (120-140˚С). However, the same bacteria produce spores of varying resistance, and some of the spores can be killed by prolonged boiling. When the spore gets into favorable conditions, it begins to germinate. At the same time, it swells, becomes richer in water, almost doubling in size. The outer shell is torn and the seedling comes out through the hole formed. In some bacilli, the activation of enzymes and the formation of a vegetative cell is completed in 40-50 minutes. Sometimes, when toxic substances accumulate in the environment, spore-bearing bacilli may lose their ability to sporulate.

Mushrooms are ancient heterotrophic organisms that occupy a special place in the general system of living nature. They can be both microscopically small and reach several meters. They settle on plants, animals, humans or on dead organic remains, on the roots of trees and grasses. Their role in biocenoses is great and varied. In the food chain, they are decomposers - organisms that feed on dead organic residues, subjecting these residues to mineralization to simple organic compounds.

Mushrooms play a positive role in nature: they are food and medicine for animals; forming a fungus root, help plants absorb water; As a component of lichens, fungi provide a habitat for algae.

Mushrooms are chlorophyll-free lower organisms, uniting about 100,000 species, from small microscopic organisms to such giants as tinder fungi, a giant puffball and some others.

In the system of the organic world, fungi occupy a special position, representing a separate kingdom, along with the kingdoms of animals and plants. They are devoid of chlorophyll and therefore require ready-made organic matter for nutrition (they belong to heterotrophic organisms). By the presence of urea in the metabolism, in the cell membrane - chitin, a reserve product - glycogen, and not starch - they approach animals. On the other hand, in the way they feed (by absorbing, not swallowing food), by unlimited growth, they resemble plants.

Mushrooms also have features that are unique to them: in almost all mushrooms, the vegetative body is a mycelium, or mycelium, consisting of filaments - hyphae.

These are thin, like threads, tubes filled with cytoplasm. The threads that make up the mushroom can be tightly or loosely intertwined, branched, grow together with each other, forming films like felt or bundles visible to the naked eye.

In higher fungi, the hyphae are divided into cells.

Fungal cells can have from one to several nuclei. In addition to nuclei, there are other structural components in cells (mitochondria, lysosomes, endoplasmic reticulum, etc.).

Structure

The body of the vast majority of fungi is built from thin filamentous formations - hyphae. Their combination forms a mycelium (or mycelium).

Branching, the mycelium forms a large surface, which ensures the absorption of water and nutrients. Conventionally, mushrooms are divided into lower and higher. In lower fungi, hyphae do not have transverse partitions and the mycelium is a single highly branched cell. In higher fungi, the hyphae are divided into cells.

The cells of most fungi are covered with a hard shell; zoospores and the vegetative body of some protozoan fungi do not have it. The cytoplasm of the fungus contains structural proteins and enzymes, amino acids, carbohydrates, and lipids not associated with cell organelles. Organelles: mitochondria, lysosomes, vacuoles containing reserve substances - volutin, lipids, glycogen, fats. There is no starch. A fungal cell has one or more nuclei.

reproduction

Fungi have vegetative, asexual and sexual reproduction.

Vegetative

Reproduction is carried out by parts of the mycelium, special formations - oidia (formed as a result of the breakdown of hyphae into separate short cells, each of which gives rise to a new organism), chlamydospores (they are formed in much the same way, but have a thicker dark-colored shell, tolerate adverse conditions well), by budding of mycelium or individual cells.

For asexual vegetative reproduction, special devices are not needed, but not many, but few descendants appear.

With asexual vegetative reproduction, the cells of the thread do not differ from their neighbors, grow into a whole organism. Sometimes, animals or environmental movement tear the hyphae apart.

It happens that when adverse conditions occur, the thread itself breaks up into separate cells, each of which can grow into a whole mushroom.

Sometimes growths form on the thread, which grow, fall off and give rise to a new organism.

Often, some cells build up a thick shell. They can withstand desiccation and remain viable for up to ten years or more, and germinate under favorable conditions.

In vegetative reproduction, the DNA of the offspring does not differ from the DNA of the parent. With such reproduction, special devices are not needed, but the number of offspring is small.

asexual

During asexual spore reproduction, the filament of the fungus forms special cells that create spores. These cells look like branches that are unable to grow and separate spores from themselves, or like large bubbles inside which spores form. Such formations are called sporangia.

In asexual reproduction, the DNA of the offspring does not differ from the DNA of the parent. Less substances are spent on the formation of each spore than on one descendant during vegetative propagation. Asexually, one individual produces millions of spores, so the fungus is more likely to leave offspring.

sexual

During sexual reproduction, new combinations of characters appear. In this reproduction, the DNA of the offspring is formed from the DNA of both parents. Fungi combine DNA in different ways.

Different ways to ensure DNA integration during sexual reproduction of fungi:

At some point, the nuclei fuse, and then the DNA strands of the parents, exchange pieces of DNA and separate. In the DNA of the descendant are areas received from both parents. Therefore, the descendant is somewhat similar to one parent, and in some ways to the other. A new combination of traits can reduce and increase the viability of offspring.

Reproduction consists in the fusion of male and female gametes, resulting in the formation of a zygote. In fungi, iso-, hetero- and oogamy are distinguished. The reproductive product of lower fungi (oospore) germinates into a sporangium in which spores develop. In ascomycetes (marsupials), as a result of the sexual process, bags (asci) are formed - unicellular structures, usually containing 8 ascospores. Bags formed directly from the zygote (in lower ascomycetes) or on ascogenous hyphae developing from the zygote. In the bag, the nuclei of the zygote merge, then the meiotic division of the diploid nucleus and the formation of haploid ascospores occur. The bag is actively involved in the distribution of ascospores.

For basidiomycetes, a sexual process is characteristic - somatogamy. It consists in the fusion of two cells of the vegetative mycelium. The sexual product is the basidium, on which 4 basidiospores are formed. Basidiospores are haploid, they give rise to haploid mycelium, which is short-lived. By fusion of the haploid mycelium, a dikaryotic mycelium is formed, on which basidia with basidiospores are formed.

In imperfect fungi, and in some cases in others, the sexual process is replaced by heterocariosis (diversity) and the parasexual process. Heterokaryosis consists in the transition of genetically heterogeneous nuclei from one segment of the mycelium to another by the formation of anastomoses or fusion of hyphae. The fusion of nuclei does not occur in this case. The fusion of nuclei after their transition to another cell is called a parasexual process.

The filaments of the fungus grow by transverse division (the filaments do not divide along the cell). The cytoplasm of neighboring cells of the fungus is a single whole - there are holes in the partitions between the cells.

Nutrition

Most mushrooms look like long filaments that absorb nutrients from the entire surface. Mushrooms absorb the necessary substances from living and dead organisms, from soil moisture and water from natural reservoirs.

Mushrooms secrete substances that break the molecules of organic substances into parts that the fungus can absorb.

But under certain conditions, it is more useful for the body to be a thread (like a mushroom), and not a lump (cyst) like a bacterium. Let's check if this is so.

Let's follow the bacterium and the growing filament of the fungus. A strong sugar solution is shown in brown, a weak one is light brown, and water without sugar is shown in white.

It can be concluded that a filamentous organism, growing, can end up in places rich in food. The longer the thread, the greater the supply of substances that saturated cells can spend on the growth of the fungus. All hyphae behave like parts of one whole, and the fungus sections, once in food-rich places, feed the entire fungus.

mold mushrooms

Mold fungi settle on moistened remains of plants, less often animals. One of the most common fungi is mucor, or capitate mold. The mycelium of this fungus in the form of the thinnest white hyphae can be found on stale bread. The hyphae of the mucor are not separated by septa. Each hypha is one highly branched cell with several nuclei. Some branches of the cell penetrate the substrate and absorb nutrients, others rise up. At the top of the latter, black rounded heads are formed - sporangia, in which spores are formed. Mature spores are spread by air currents or with the help of insects. Once in favorable conditions, the spore germinates into a new mycelium (mycelium).

The second representative of mold fungi is penicillium, or gray mold. Mycelium penicilla consists of hyphae separated by transverse partitions into cells. Some hyphae rise up, and branchings resembling brushes form at their end. At the end of these branches, spores are formed, with the help of which the penicillium multiplies.

yeast mushrooms

Yeasts are single-celled immobile organisms of oval or elongated shape, 8-10 microns in size. They do not form true mycelium. The cell has a nucleus, mitochondria, many substances (organic and inorganic) accumulate in vacuoles, redox processes occur in them. Yeasts accumulate volutins in cells. Vegetative propagation by budding or division. Sporulation occurs after repeated reproduction by budding or division. It is made easier with a sharp transition from abundant nutrition to a small one, with the supply of oxygen. In the cell, the number of spores is paired (usually 4-8). In yeast, the sexual process is also known.

Yeast fungi, or yeast, are found on the surface of fruits, on plant residues containing carbohydrates. Yeasts differ from other fungi in that they do not have a mycelium and are single, in most cases oval cells. In a sugary environment, yeast causes alcoholic fermentation, as a result of which ethyl alcohol and carbon dioxide are released:

C 6 H 12 O 6 → 2C 2 H 5 OH + 2CO 2 + energy.

This process is enzymatic, proceeds with the participation of a complex of enzymes. The released energy is used by yeast cells for life processes.

Yeast reproduces by budding (some species by fission). When budding, a bulge resembling a kidney is formed on the cell.

The nucleus of the mother cell divides, and one of the daughter nuclei passes into a bulge. The bulge grows rapidly, turns into an independent cell and separates from the mother. With very rapid budding, the cells do not have time to separate, and as a result, short fragile chains are obtained.

At least ¾ of all fungi are saprophytes. The saprophytic mode of nutrition is associated mainly with products of plant origin (the acidic reaction of the environment and the composition of organic substances of plant origin are more favorable for their life).

Symbiont fungi are associated mainly with higher plants, bryophytes, algae, less often with animals. An example would be lichens, mycorrhiza. Mycorrhiza is the cohabitation of a fungus with the roots of a higher plant. The fungus helps the plant to assimilate hard-to-reach humus substances, promotes the absorption of mineral nutrition elements, helps with its enzymes in carbohydrate metabolism, activates the enzymes of a higher plant, and binds free nitrogen. From the higher plant, the fungus apparently receives nitrogen-free compounds, oxygen, and root secretions that promote the germination of spores. Mycorrhiza is very common among higher plants; it is not found only in sedge, cruciferous and aquatic plants.

Ecological groups of fungi

soil mushrooms

Soil fungi are involved in the mineralization of organic matter, the formation of humus, etc. In this group, fungi are distinguished that enter the soil only during certain periods of life, and fungi of the rhizosphere of plants that live in the zone of their root system.

Specialized soil fungi:

• coprophylls- mushrooms that live on soils rich in humus (dung heaps, places where animal droppings accumulate);
• keratinophils- mushrooms that live on hair, horns, hooves;
• xylophytes- mushrooms that decompose wood, among them there are destroyers of living and dead wood.

house mushrooms

House mushrooms - destroyers of wooden parts of buildings.

aquatic mushrooms

These include the group of mycorrhizal symbiont fungi.

Mushrooms that develop on industrial materials (on metal, paper and products from them)

cap mushrooms

Hat mushrooms settle on humus-rich forest soil and from it get water, mineral salts and some organic substances. Part of the organic matter (carbohydrates) they receive from trees.

Mushroom is the main part of every mushroom. Fruiting bodies develop on it. The cap and stem consist of mycelium filaments tightly adjacent to each other. In the stem, all the threads are the same, and in the cap they form two layers - the upper one, covered with a skin colored with different pigments, and the lower one.

In some mushrooms, the lower layer consists of numerous tubules. Such mushrooms are called tubular. In others, the lower layer of the cap consists of radially arranged plates. Such mushrooms are called lamellar. On the plates and on the walls of the tubules, spores are formed, with the help of which the fungi multiply.

The hyphae of the mycelium braid the roots of trees, penetrate into them and spread between the cells. Between the mycelium and the roots of plants, a cohabitation useful for both plants is established. The fungus supplies plants with water and mineral salts; replacing the root hairs on the roots, the tree yields to it some of its carbohydrates. Only with such a close connection of the mycelium with certain tree species is it possible to form fruiting bodies in cap mushrooms.

Spore formation

In the tubules or on the plates of the cap, special cells are formed - spores. Ripened small and light spores spill out, they are picked up and carried by the wind. They are carried by insects and slugs, as well as squirrels and hares that eat mushrooms. The spores are not digested in the digestive organs of these animals and are thrown out along with the droppings.

In moist, humus-rich soil, fungal spores germinate, from which mycelium filaments develop. Mycelium, arising from a single spore, can form new fruiting bodies only in rare cases. In most species of fungi, fruiting bodies develop on myceliums formed by merged cells of filaments originating from different spores. Therefore, the cells of such a mycelium are binuclear. The mushroom picker grows slowly, only having accumulated reserves of nutrients, it forms fruiting bodies.

Most species of these fungi are saprophytes. They develop on humus soil, dead plant residues, some on manure. The vegetative body consists of hyphae that form a mycelium located underground. In the process of development, umbrella-like fruiting bodies grow on the mycelium. The stump and hat consist of dense bundles of mycelium filaments.

In some mushrooms, on the underside of the cap, plates diverge radially from the center to the periphery, on which basidia develop, and in them spores are a hymenophore. Such mushrooms are called lamellar. Some species of fungi have a veil (film of infertile hyphae) that protects the hymenophore. When the fruiting body ripens, the veil breaks and remains in the form of a fringe along the edges of the cap or ring on the leg.

In some fungi, the hymenophore has a tubular shape. These are tubular mushrooms. Their fruiting bodies are fleshy, quickly rot, easily damaged by insect larvae, eaten by slugs. Cap mushrooms reproduce by spores and parts of the mycelium (mycelium).

The chemical composition of mushrooms

In fresh mushrooms, water makes up 84-94% of the total mass.

Mushroom proteins are digested only by 54-85% - worse than the proteins of other plant products. Assimilation is hindered by the poor solubility of proteins. Fats and carbohydrates are digested very well. The chemical composition depends on the age of the fungus, its condition, species, growing conditions, etc.

The role of mushrooms in nature

Many mushrooms grow together with the roots of trees and grasses. Their cooperation is mutually beneficial. Plants give sugar and proteins to fungi, and fungi destroy dead plant remains in the soil and absorb water with mineral substances dissolved in it by the entire surface of the hyphae. Roots fused with fungi are called mycorrhiza. Most trees and grasses form mycorrhiza.

Fungi play the role of destroyers in ecosystems. They destroy dead wood and leaves, plant roots and animal carcasses. They turn all dead remains into carbon dioxide, water and mineral salts - into what plants can absorb. When fed, mushrooms gain weight and become food for animals and other fungi.

mushroom spores

Fungal spores are designed to reproduce. They are one or more cells with microscopic dimensions - from 1 to 100 microns. The spores of most fungal species contain extremely few nutrients, rare of them survive and, once in favorable conditions, germinate, giving rise to the mycelium of a young fungus. But the death of most spores is compensated by the formation of their huge number. For example, the causative agent of stem rust of cereal plants forms up to 10 billion spores on one barberry bush in spring and June, the fruiting body of a tinder fungus produces up to 30 billion spores, champignons form about 40 billion spores per hour.

It is generally accepted that spores are classified by origin and function in the life of fungi into two broad groups:

a) spores of asexual reproduction (mitospores);

b) spores of sexual reproduction (meiospores).

During the formation of mitospores, mitotic division of the cell nucleus occurs with the preservation of the number of chromosomes; meiospores - meiosis, characterized by a decrease in the number of chromosomes by half.

Mitospores and meiospores perform different functions in the life of fungi. Mitospores are intended mainly for the mass distribution of fungi during the vegetative period, without recombination of hereditary qualities. Meiospores are spores of sexual reproduction. Their appearance is associated with the germination of a zygote - a cell formed during the sexual process from two parental cells. In the process of germination of the zygote and the formation of spores of sexual reproduction, the recombination (redistribution) of the characteristics of the parent organisms occurs, and the diversity of the offspring increases.

In many species of fungi, both mitospores and meiospores are formed in the life cycle. For example, in many marsupial fungi - causative agents of ergot, powdery mildew of plants, apple scab, etc. mitospores are formed throughout the entire growing season and perform the function of re-infecting plants, and meiospores are formed after wintering and provoke primary infection of plants.

A large group of fungi does not have mitospores in the development cycle, like many cap mushrooms, tinder fungi, gasteromycetes, and some types of discomycetes (morels, stitches). In such cases, meiospores take on the functions of mitospores and serve for the mass dispersal of fungi.

Formation

The formation of mitospores in most forms of fungi occurs inside special cells - sporangia or externally on the branches of aerial mycelium. The first types of spores are called sporangiospores, the second - conidia. Sporangiospores are immobile and passively carried, may have flagella and with their help actively move in the aquatic environment. Motile spores are called zoospores. Reproduction by zoospores is carried out only in the presence of a drop-liquid medium.

Sporangiospores, like zoospores, serve for the wide distribution of fungi. They contain a small amount of nutrients and are not able to maintain their viability for a long time. In one sporangium, up to several tens of thousands of spores can form. An increase in the production of sporangiospores is achieved due to additional branches of sporangiophores and an increase in the number of sporangia. Therefore, for the formation of a large sporangium with many sporangiospores, a longer period is needed than for the mass formation of conidia. This explains the fact that most fungi reproduce asexually with the help of conidia.
Conidia are formed in higher fungi with cellular mycelium on the hyphae of aerial mycelium - conidiophores. They are usually very small (from 1 to 10-15 microns) and form in huge numbers. Unlike sporangiospores, conidia can remain viable for a long time under adverse conditions without germinating. Conidia are released both actively and passively as they mature. In the process of evolution, they have formed multiple adaptations that facilitate their distribution. Some conidia have a dry surface, making them easily carried by the wind; others are covered with mucus and are well tolerated by insects or water, etc.

Meiospores, like mitospores, are extremely diverse in fungi. They are formed inside or on the surface of special cells, which are called, respectively, bags and basidia. The bags are located in the fruiting bodies of mushrooms and are well protected from the effects of adverse environmental factors. In fungi from the group of ascomycetes, ascospores are formed, in basidiomycetes - basidiospores having a different structure.