Representatives of unicellular fungi are, for example, yeast. About 500 species of yeast fungi are known. Yeasts are found in nature on the surface of plants, in the nectar of flowers, on fruits, in the sap of trees, and in the soil. They do not form typical mycelium. These microscopic fungi consist of a single cell shaped like a ball. Yeast reproduces by budding: a protrusion forms on the body of the fungus (like a bud), which enlarges, separates from the mother’s body (buds) and leads an independent lifestyle. Budding yeast cells look like branching chains. For a long time, people have been using yeast to make bread. Yeast grows quickly, which is determined by its unusually high metabolic rate. At the same time, they significantly change the chemical composition of the environment. The most famous process they carry out is alcoholic fermentation. Yeast feeds on sugar, turning it into alcohol. This releases carbon dioxide, which helps the dough rise, making it light and porous. People use some yeast fungi in brewing, winemaking and as protein feed in livestock. Pasechnik V.V. Biology. 5th grade // Bustard. Ponomareva I. N., Kornilova O. A., Kuchmenko V. S. Biology. 6th grade // IC VENTANA-GRAF. Viktorov V. P., Nikishov A. I. Biology. Plants. Bacteria. Fungi and lichens. 7th grade // Humanitarian Publishing Center “VLADOS”.

Mushrooms are a terrible force. They can kill and save a person. Some of them devour our food or destroy human organs, but without the work of the subjects of this Kingdom, the cycle of minerals and organic substances on Earth is impossible. Prominent representatives of this two-faced taxon are mucor and penicillium.

Penicillium is a mold fungus of the Ascomycetes department, that is, marsupial fungi.

By the way, the most expensive representatives of the department are truffles, and morels have become the talk of the town.

Mukor is a mold fungus of the Zygomycetes division.

Comparison

Penicillium is one of the genera of the marsupial fungi department. In nature, these organisms settle on the ground and on living plants, forming a moldy coating of amazing emerald and azure color.

Mukor is one of the genera of lower mushrooms. These organisms live in the upper layers of the soil.

Under appropriate conditions - warm and high humidity, they quickly appear on the surfaces of various food products and any other creatures of an organic nature.

In this case, the substrate acquires a characteristic pale white coating, which darkens over time.

Mucor can cause diseases - mucormycosis in humans and animals, which primarily affect the dermis and respiratory organs. When the process generalizes, the fungus begins to spread throughout the body, using brain cells as a base substrate.

Penicillium has antibacterial properties noted by Ernst Duchenne and Alexander Fleming, and therefore became the basis for the manufacture of the antibiotic penicillin.

The body of a mature mucor is not differentiated into cells.

Its mycelium resembles a single cell, like a giant octopus, containing many nuclei. The color of this formation is whitish, sometimes beige or soft gray.

From this body-mycelium, individual sporangiophores sprout. At their tops, dark gray, anthracite sporangia are formed, which contain spores. With increased air humidity, the sporangium shell dissolves, and thousands of new spores spill out onto the substrate.

Mucors are capable of sexual reproduction - zygogamy, when two neighboring multinucleate giant cells interbreed, and can also increase the number of individuals of the species by vegetative means.

At the same time, hyphae-stolons stretch in different directions from the mother cell. Having found a suitable substrate, they release rhizoids, attach themselves and detach from the parent organism.

The body of the penicillium consists of many cells.

The structure and activity of yeast

Conidiophores grow from the mycelial hyphae. Their tops are branched, giving the mushroom a resemblance to a child's hand. At the tips of these “handles” single-celled spores – conidia – are formed. Under favorable conditions (high humidity and temperature), spores fall into the substrate and germinate. They are the main way penicillium reproduces.

Individual mucor mushrooms, as a powerful source of enzymes, are used in the process of fermentation of products.

With the help of Chinese, snail-shaped and racemose mucor, dry or “Chinese” yeast, mash, soy cheese, and ethyl alcohol are produced from potatoes. Ramannian mucor is the main raw material for the production of the antibiotic ramycin.

Penicill is the basic raw material for the production of the antibiotic penicillin.

In nature, mucors and penicilliums are typical saprophytes, one of the most important links in the stage of decomposition and mineralization of organic remains.

Conclusions TheDifference.ru

1. Both mushrooms belong to different divisions of the Kingdom of Fungi.
2. Mucor is able to develop on a larger number of types of substrates - soil, living and dead flesh, plants and animals.

   Penicillium prefers soil and living plant organisms; rarely settles on food products of a plant nature.

3. The color of mucor mycelium is white-gray-anthracite.

   The color of penicillium mycelium is azure, grassy, ​​emerald.

4. The body of mucor is unicellular with many nuclei, while that of penicillium is multicellular.
5. Mucor reproduces sexually, vegetatively and by spores, while penicillium prefers to reproduce exclusively by spores.
6. Mucor has more applications - in the food industry and pharmacology, penicillium is used to make the antibiotic penicillin.

Mushrooms have long been used by humans as food; recently, artificially grown champignons, shiitake, oyster mushrooms, etc. have become widespread.

The meaning of yeast, penicillium in nature and human life

Since mushrooms are undemanding to the substrate, mushroom growing solves the very important problem of recycling waste from the wood processing, food industries and agriculture, since they are grown on sawdust, sunflower husks or straw.

In the food industry, mushrooms are used in the production of lactic acid products, in baking, winemaking and brewing, in the production of meat and sausage products, and in the production of citric acid.

For example, the production of the famous French cheeses Roquefort and Brie is impossible without mold fungi, while the production of kefir and bread uses yeast that releases carbon dioxide during the fermentation process.

Equally important is the production of medicinal drugs - antibiotics - from mushrooms.

Although currently most of these biologically active substances are obtained from other microorganisms, it is the fungal antibiotics - penicillins and cephalosporins that ensure the survival of patients even in such severe conditions as peritonitis or sepsis. Recently discovered antibiotics - cyclosporins - artificially reduce the body's immunity, which has made it possible to put organ transplantation on a new basis.

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Level A assignments

Choose one correct answer from the four given.
A1. The lower fungi include
2) Zygomycotes

A2. Yeasts belong to the fungi department
1) Asmikota

A3. The science of mushrooms is called
2) Mycology

A4. In fungal cells
3) Contains only one core each

A5. The combination of stems and caps of mushrooms is called
4) Fruiting body

Boletus and porcini mushrooms are classified as mushrooms
2) Symbionts

A7. Lichen is a complex organism consisting of
1) Mushroom and algae

504 Gateway Time-out

The thallus of lichens is most complexly structured
2) Bushy

Level B assignments

Choose three correct answers from the six given.
IN 1. Signs that bring mushrooms closer to animals
1) The presence of chitin in the cell membrane
2) Glycogen storage
4) Urea formation

Lichen is
1) Cladonia
3) Icelandic moss
4) Cetraria
Match the contents of the first and second columns.
AT 3. Establish a correspondence between the departments of mushrooms and their representatives.

Establish a correspondence between the types of lichen thallus and their characteristics.

Establish the correct sequence of biological processes, phenomena, and practical actions.
AT 5. Determine the systematic position of the camelina, placing the taxa in the correct sequence, starting with the species.
A) Mushrooms
B) Basidiomycota
B) Ryzhik

Mukor. Class Zygomycetes

1. The mycelium is a single cell, nonseptate, multinucleate, and has the appearance of white mold.

Forms numerous vertical sporangiophores with black sporangia. In sporangia, up to 10 thousand multinucleate spores are formed endogenously (inside).

3. Finding suitable conditions, the spores germinate and give rise to a new mucor mycelium. This is how asexual reproduction of mucor occurs.

4. When the substrate is depleted, mucor proceeds to sexual reproduction.

Penicillium (tassel) Class Ascomycetes

Saprotrophic soil and mold fungi that settle on bread, vegetables and other products.

The mycelium is branching, divided by transverse partitions (septated), which allows the hypha, in case of damage, to lose less cellular content and causes greater survival of ascomycetes compared to zygomycetes.

At first it looks like a white cobwebby coating, and then acquires a greenish or bluish tint.

Conidiophores rise upward from the mycelium, the ends of which form a brush. At the tip of each branch, a chain of rounded spores and conidia is formed exogenously (outwardly). They are carried by air currents and give rise to new mycelium.

Sexual reproduction occurs rarely, under unfavorable conditions.

In this case, the fusion of two specialized mycelial cells that are not differentiated into gametes occurs. The zygote produces a sac (ask) in which ascospores develop. When favorable conditions (humidity) occur, the bag swells and the spores are scattered with force over a long distance.

Yeast, its structure and reproduction

Yeast belongs to the group of unicellular fungi that have lost their mycelial structure, because their habitats have become liquid or semi-liquid substrates containing large quantities of organic substances.

The group of yeast fungi includes 1500 species

In nature yeast are widespread and live on substrates rich in sugars, feeding on flower nectar, plant juices, dead phytomass, etc. Yeasts can live in soil and water, and in the intestines of animals.

Yeasts are fungi that live for all or most of their life cycle in the form of individual, single cells.

The size of yeast cells averages from 3 to 7 microns in diameter, but there are some species whose cells can reach 40 microns. Yeast cells are nonmotile and oval in shape. Although yeasts do not form mycelium, they exhibit all the signs and properties of mushrooms.

They can be of various shapes: elliptical, oval, spherical and rod-shaped. Cell length ranges from 5 to 12 µm, width - from 3 to 8 µm.

The shape and size of yeast cells are variable and depend on the genus and species, as well as on cultivation conditions, the composition of the nutrient medium and other factors. Young cells are more stable, so young cultures are used to characterize yeast. A yeast cell consists of a cell membrane, an adjacent cytoplasmic membrane, cytoplasm or protoplasm, inside which organelles and inclusions (reserve substances) are located in the form of droplets of fat, grains of glycogen and volutin.

Yeast cell shapes: a - elliptical; b - oval; c - slightly elongated; d - ovoid with spores; d - lemon-shaped; e - elongated (false mycelium); g - round; h - elliptical with spores.

Since ancient times, certain types of yeast have been used by humans in the production of wine, beer, bread, kvass, in the industrial production of alcohol, etc.

Some types of yeast are used in biotechnology due to their important physiological properties.

Mushrooms (structure, role in nature). Yeast (human use)

In modern production, using yeast, food additives, enzymes, xylitol are obtained, and water is purified from oil contamination. But there are also negative properties of yeast. Some types of yeast can cause diseases in humans because they are facultative, or opportunistic, pathogenic microorganisms. Such diseases include candidiasis, cryptococcosis, and pityriasis.

Mushroom propagation

Fungi reproduce asexually and sexually.

Asexual reproduction is carried out either vegetatively, that is, by parts of the mycelium, or by spores. Spores develop in sporangia that arise on specialized hyphae - sporangiophores, rising above the substrate (soil).

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Molds and yeasts

Molds appeared on our planet about 200 million years ago. Mold can both take life and save you from death. Mold looks beautiful, but does not evoke any feelings other than disgust. Molds are a variety of fungi that form branching mycelia without large fruiting bodies. Mold is a micromycete. These are mushrooms and fungiformes, having microscopic sizes.

Molds are widespread in nature; they grow almost everywhere. Large colonies grow on nutrient media at high temperatures and high humidity, and mold growth is not limited as long as food is available. Molds are distinguished by their unpretentiousness to their environment and food.

Fig.1. The structure of mycelium and vegetative reproductive organs of mold fungi

1 - unicellular (mukor); 2 - multicellular (penicillium); 3 - a- penicillium conidiophore with conidia; b — Aspergillus conidiophore with conidia; c - sporangiophorus mucor with sporangia filled with spores

In the structure of mold fungi, branching hyphae forming mycelium, or mycelium, are distinguished.

Mold fungi are extremely diverse, but they are all characterized by typical features. The mycelium (mycelium) of mold fungi is the basis of their vegetative body and looks like a complex of branching thin threads (hyphae).

Fungal hyphae are located on the surface or inside the substrate on which the fungus has settled. In most cases, molds form large myceliums that occupy a large surface area. Lower fungi have noncellular mycelium, whereas in most mold fungi the mycelium is divided into cells.

Reproduction of mold fungi

Fungi can reproduce in a variety of ways. The simplest, characteristic of all mushrooms, is reproduction by parts of the mycelium.

Each part of the mycelium (mycelium), once on a new area of ​​the substrate, under favorable circumstances, becomes independent and develops as a whole organism, and the part of the mycelium, which is immersed in the nutrient substrate, plays a major role in providing the mold fungus with nutrients, moisture and minerals. The airy part, rising above the surface of the substrate, as a rule, serves to form various bodies with the help of which molds reproduce (oidia, spores, conidia, etc.).

Oidia are bodies that are parts of the mycelium.

They are formed by some multicellular fungi, in which the mature mycelium breaks up into many small sections that acquire a dense shell.

Spores are bodies of various shapes, measuring up to several microns; usually located at the ends of the hyphae of the aerial part of the mycelium, inside special oval and semicircular formations - sporangia.

Angiospore spores are formed by the breakdown of the multinucleate cytoplasm of a young sporangium into many separate sections, which are gradually covered with their own membrane and turn into spores.

The threads of aerial mycelium bearing sporangia are called sporangiophores.

This formation of spores is characteristic of unicellular fungi. In multicellular organisms, so-called exospores are formed, i.e. external, or external, which are more often called conidia, and the aerial hyphae that carry them are called conidiophores.

Conidia are formed by separating directly from conidiophores or special cells located at their top. These cells are usually oblong in shape and are called sterigmata.

Conidia are located on conidiophores (or on sterigmata) singly, in chains, etc.

Sporangiophores and conidiophores form a visible fluffy coating on the surfaces of materials affected by fungi. Its different colors (green, black, olive, pink, white, gray, etc.) depend on the color of conidia, spores, oidia, which are formed in enormous quantities when the fungi reach physiological maturity.

Mushroom mycelium is usually colorless.

Many fungi, reproducing in one way or another vegetatively, can also reproduce sexually under suitable development conditions. This process is different for different mushrooms. However, special fruiting bodies are always formed, in some cases reaching enormous sizes (cap, lamellar, tubular and other mushrooms found in nature are the fruiting bodies of mold fungi).

Sexual spores are located on plates or in containers - bags.

An example of the latter are various types of raincoats and stitching. Fungi that are capable of reproducing Chlamydospores and fungal sclerotia sexually are called perfect.

Some mushrooms do not reproduce sexually at all. They are classified as imperfect. Knowledge of the structural features of the mycelium, organs of vegetative reproduction, and the structure of fruiting bodies is necessary in practical work to recognize specific pathogens of certain processes.

Many fungi, when unfavorable conditions occur, are capable of forming dormant stages in the form of so-called sclerotia.

These are strong, hard on the surface, usually dark, and inside white nodules of various sizes and shapes, formed from tightly intertwined hyphae.

Sclerotia, finding themselves in conditions favorable for development, germinate and form one or another (depending on the type of fungus) reproductive organs. They often form in the ears of cereals. Another resting stage is chlamydospores. When they form, the cytoplasm inside the hyphae collects in the form of lumps, forming a new shell, usually thick and colored, and the hyphae become like chains or beads consisting of chlamydopores.

Sometimes chlamydospores form only at the ends of hyphae. The multicellular structure, differentiation of vital functions between parts of the fungus - aerial and deep mycelium - indicate that molds are more highly organized, complex organisms compared to bacteria.

Mushroom nutrition

The cells of mold fungi do not have chlorophyll, and therefore these fungi require ready-made organic substances for nutrition.

Molds feed by absorbing organic matter. Moreover, first the mold secretes digestive enzymes to digest food, and then absorbs the organic compounds broken down into simpler ones. Since molds do not have the ability to move around to search for food, they “live” in the food itself.

Fig.2.

Yeast meaning:

Mold Fungus aspergillus fumigatus

There are many types of mold found in nature, such as Penicillium spp, Mycorales, Aspergillus, Fusarium, Dematiaceae, Saccharomycetaceae, etc. Fungi of the genus Penicillum are of great importance for humans. Penicillium is a green mold that grows on plant substrates, including food products.

Penicillium produces the antibiotic penicillin, the world's first antibacterial drug discovered. It is also important for humans to use yeasts belonging to the Saccharomycetes fungi on the farm. Yeasts are fungi that do not form classical mycelium, and their vegetative cells reproduce by budding or division.

Yeasts can live as individual single cells throughout their entire life cycle. Since ancient times, yeast has been widely used by humans, as these fungi are involved in the process of alcoholic fermentation. This property of yeast is used in the production of alcohol and alcohol-containing products, winemaking, baking, confectionery, and the production of feed protein for livestock nutrition.

Many types of molds have pathogenic properties, that is, they can cause diseases in humans, animals, and plants.

Other types of mold harm human households because they spoil food products, including vegetables and fruits, during long-term storage, and cause damage to timber and fabrics.

Yeast, its structure and reproduction

Yeasts are single-celled, non-motile organisms. They can be of various shapes: elliptical, oval, spherical and rod-shaped. Cell length ranges from 5 to 12 µm, width - from 3 to 8 µm. The shape and size of yeast cells are variable and depend on the genus and species, as well as on cultivation conditions, the composition of the nutrient medium and other factors.

Young cells are more stable, so young cultures are used to characterize yeast. A yeast cell consists of a cell membrane, an adjacent cytoplasmic membrane, cytoplasm or protoplasm, inside which organelles and inclusions (reserve substances) are located in the form of droplets of fat, grains of glycogen and volutin.

Fig.3.

Diagram of the structure of a yeast cell

1 - fissile nucleus; 2 - glycogen; 3 - volutin; 4 - mitochondria

Yeast belongs to the class of marsupial fungi (Ascomycetes - ascomycetes) to the subclass of protozoan marsupials (Protoascales - protoasks). The classification of yeast is based on the method of reproduction and some physiological characteristics. The main systematic feature is the ability to form spores. Based on this characteristic, yeasts are divided into two groups: sporogenic yeast - yeast capable of forming spores, and asporogenic yeast - not forming spores, i.e.

i.e. without sexual reproduction.

According to some researchers, the second group of yeasts should be classified as imperfect fungi (Fungi imperfecti), although the loss of the ability to sexually reproduce is secondary, and they can also be classified as marsupial fungi.

The classification of sporogenic fungi was proposed in 1954 by V.I. Kudryavtsev. It is based on the method of vegetative propagation.

V.I. Kudryavtsev proposes to combine all yeasts into one order of unicellular fungi (Unicellomycetales - unicellomycetes).

He divides sporogenous yeasts into three families based on vegetative reproduction:

Family Saccharomycetaceae (saccharomycetaceae) - reproduce by budding.

This family includes the genera Saccharomyces (saccharomyces), which has the greatest practical importance, Pichia (pyhia), Hasenula (hansenula), etc. (17 genera in total). They differ in the shape of the spores and the method of their formation and germination.

Family Schizosaccharomycetaceae (schizosaccharomycetaceae) - reproduce by division. This family includes two genera: Schizosaccharomyces (schizosaccharomyces) and Octosporomyces (octosporomyces).

Family Saccharomycodaceae (saccharomycodaceae) - reproduction begins with budding and ends with division.

The main genera of this family are Saccharomycodes and Hanseniaspora.

Asporogenic yeasts are classified according to the system of J. Lodder and Kroeger van Rij, proposed in 1952. The classification is based on the ability of microorganisms to form false mycelium and the ability to ferment.

The main genera of this group are Candida (candida) and Torulopsis (torulopsis).

Yeast can reproduce vegetatively (by budding or fission) and by spores. During budding, a tubercle appears on the mother cell - a bud, which grows and, having reached a certain size, separates from the mother cell.

Under favorable conditions, the budding process lasts about 2 hours. In some yeasts, daughter cells do not separate from the mother cells, but remain connected, forming false mycelium (membranous yeast).

In most yeasts, under unfavorable conditions, for example, during a sharp transition from good nutrition to poor nutrition, spore formation occurs, although there are asporogenic yeasts that never form spores (Candida, Torulopsis). Spores are mostly formed asexually, although the cell nucleus undergoes reduction division before this, so that the spores have a haploid (single) set of chromosomes.

From 2 to 8 ascospores appear in the cell, which, when mature, can continue to reproduce by budding, giving a weakened haploid generation. As a result of the fusion of two haploid ascospores, a diploid zygote is formed, which subsequently gives a normal generation. The formation of sexual spores is observed in the yeast Zigosaccharomyces (zygosaccharomyces).

In them, the formation of spores is preceded by cell fusion (copulation).

Practical significance of yeast

The yeasts Saccharomyces cerevisiae and Saccharomyces ellipsoideus are of greatest practical importance. Yeast Sacch. cerevisiae can be round or oval in shape. Widely used in baking, brewing, kvass and for the production of alcohol. Under the influence of environmental conditions, certain types of yeast acquired some distinct characteristics.

These varieties of yeast are usually called races. Various industries use their own races of yeast. The alcohol industry, for example, uses races XII, XV, II, Ya. M, etc. They have the ability to actively ferment sugars at a temperature of 28-30 ° C and are relatively resistant to alcohol.

To prepare beer, races with slow fermentation at relatively low temperatures (4-10°C) are used, giving the drink an aroma and a low alcohol content.

In baking, races are used that have rapid reproduction, fermentation energy and lifting force.

Yeast Sacch. ellipsoideus (Sacch. vini). This group of yeasts is ellipsoidal in shape.

They are most often used in winemaking. There are several races with the properties to give wines a characteristic taste and aroma (bouquet). Representatives of the Sacch group of yeasts. lactis cause alcoholic fermentation in fermented milk products.

Along with useful representatives, there are species from the genus Saccharomyces (for example, Sacch.

Pasteurianum, Sacch. intermedius, Sacch. validus, Sacch. turbidans), which are pests of brewing production. When they develop in beer, they give it an unpleasant taste and smell, and the drink turns out cloudy. The class of ascomycetes includes a number of yeasts and yeast-like organisms that have lost the ability to form spores. Some of them cause damage to raw materials and finished food products.

The boundaries of the group are not clearly defined: many fungi, capable of vegetative reproduction in a unicellular form and therefore identified as yeast, at other stages of the life cycle form developed mycelium, and in some cases macroscopic fruiting bodies. Previously, such fungi were classified as a special group of yeast-like fungi, but now they are all usually considered together with yeast. 18S rRNA studies have shown a close relationship with typical yeast species, capable of growth only as mycelium.

Yeast cells typically measure 3-7 microns in diameter. There is evidence that some species are capable of growing up to 40 microns.

Yeast is of great practical importance, especially baker's or brewer's yeast ( Saccharomyces cerevisiae). Some species are facultative and opportunistic pathogens. The yeast genome has now been completely deciphered. Saccharomyces cerevisiae(they became the first eukaryotes whose genome was completely sequenced) and Schizosaccharomyces pombe.

Story

The Russian word “yeast” has a common root with the words “trembling”, “trembling”, which were used to describe the foaming of liquid that often accompanies fermentation carried out by yeast. English word " yeast"(yeast) comes from Old English " gist», « gyst", which means "foam, boil, give off gas."

Yeast is probably one of the most ancient "house organisms". For thousands of years people have used them for fermentation and baking. Archaeologists have found millstones and bakeries, as well as images of bakers and brewers, among the ruins of ancient Egyptian cities. It is assumed that the Egyptians began brewing beer 6000 BC. e., and by 1200 BC. e. mastered the technology of baking yeast bread along with baking unleavened bread. To start fermenting the new substrate, people used the remains of the old one. As a result, yeast selection took place in various farms for centuries and new physiological races not found in nature were formed, many of which were even initially described as separate species. They are the same products of human activity as varieties of cultivated plants.

Louis Pasteur - scientist who established the role of yeast in alcoholic fermentation

• Saccharomycotina
• Taphrinomycotina
  • Schizosaccharomycetes

• Urediniomycetes
  • Sporidiales

Features of metabolism

Yeasts are chemoorganoheterotrophs and use organic compounds both for energy and as a carbon source. They need oxygen for respiration, but in its absence, many species are able to obtain energy through fermentation with the release of alcohols (facultative anaerobes). Unlike bacteria, yeasts are not obligate anaerobes that die in the presence of oxygen in the environment. By passing air through the fermenting substrate, the yeast stops fermenting and begins to respire (since this process is more efficient), consuming oxygen and releasing carbon dioxide. This accelerates the growth of yeast cells ( Pasteur effect). However, even with access to oxygen, in the case of a high glucose content in the medium, the yeast begins to ferment it ( Crabtree effect).

Yeast is quite demanding regarding nutritional conditions. Under anaerobic conditions, yeast can only use carbohydrates as an energy source, mainly hexoses and oligosaccharides built from them. Some species ( Pichia stipitis, Pachysolen tannophilus) also absorb pentoses, for example, xylose. Schwanniomyces occidentalis And Saccharomycopsis fibuliger capable of fermenting starch, Kluyveromyces fragilis- inulin. Under aerobic conditions, the range of digestible substrates is wider: in addition to carbohydrates, there are also fats, hydrocarbons, aromatic and one-carbon compounds, alcohols, and organic acids. Many more species are capable of using pentoses under aerobic conditions. However, complex compounds (lignin, cellulose) are not available to yeast.

Ammonium salts can be sources of nitrogen for all yeasts; approximately half of the species have nitrate reductase and can metabolize nitrates. The pathways for assimilation of urea are different in ascomycete and basidiomycete yeasts. Ascomycetes first carboxylate it, then hydrolyze it, while basidiomycetes immediately hydrolyze it with urease.

For practical use, the products of secondary metabolism of yeast, released in small quantities into the environment, are important: fusel oils, acetoin (acetylmethylcarbinol), diacetyl, butyraldehyde, isoamyl alcohol, dimethyl sulfide, etc. The organoleptic properties of products obtained with yeast depend on them.

Spreading

Yeast habitats are associated primarily with sugar-rich substrates: the surface of fruits and leaves, where they feed on intravital plant secretions, flower nectar, wound plant juices, dead phytomass, etc., but they are also common in the soil (especially in litter and organic horizons) and natural waters. Yeast (b. Candida, Pichia, Ambrosiozyma) are constantly present in the intestines and passages of xylophages (wood-eating insects), rich yeast communities develop on leaves affected by aphids. Representatives of the genus Lypomyces are typical soil inhabitants.

Life cycle

A distinctive feature of yeast is the ability to reproduce vegetatively in a single-celled state. When compared to the life cycles of fungi, this appears as the budding of spores or zygotes. Many yeasts are also capable of implementing a sexual life cycle (its type depends on affinity), which may also include mycelial stages.

In some yeast-like fungi that form mycelium, it can disintegrate into cells (arthrospores). This is childbirth Endomyces, Galactomyces, Arxula, Trichosporon. In the last two, after formation, arthrospores begin to budding. Trichosporon also forms vegetative endospores inside mycelial cells.

Ascomycete yeast cycles

Life cycle of ascomycete haplo-diploid yeast.

The most characteristic type of vegetative propagation for unicellular ascomycete yeasts is budding, only Schizosaccharomyces pombe They reproduce not by budding, but by binary fission. The location of the bud is an important diagnostic feature: polar budding due to the formation of budding scars leads to the formation of apicular (lemon-shaped, Saccharomycodes, Hanseniaspora, Nadsonia) and pear-shaped ( Schizoblastosporion) cells; multilateral does not modify the shape of the cell ( Saccharomyces, Pichia, Debaryomyces, Candida). At birth Sterigmatomyces, Kurtzmanomyces, Fellomyces budding occurs on long outgrowths (sterigmata).

Budding in ascomycete yeasts is holoblastic: the cell wall of the mother cell softens, bends outward and gives rise to the cell wall of the daughter cell.

Often, especially in ascomycete yeast genera Candida And Pichia, the cells do not diverge after budding and form pseudomycelium, which differs from the true one by clearly visible constrictions at the site of the septa and is shorter than the previous terminal cells.

Yeast can change their mating type through DNA recombination. This change in cells occurs at a frequency of approximately 10-6 per cell. In addition to the mat locus, the cell also contains a copy of genes mat a And mat α: HMR(Hidden MAT Right) and HML (Hidden MAT Left) respectively. But these loci are in a silent state. The cell replaces a working locus mat for a copy. In this case, a copy is taken from the locus that is in the opposite allelic state. The gene is responsible for this process BUT. This gene is active only in the haploid state. It encodes endonucleases that cut DNA at the mat locus. Exonucleases then remove the mat region and replace it with a copy of HMR or HML.

Application

Some types of yeast have long been used by humans in the preparation of bread, beer, wine, kvass, etc. In combination with distillation, fermentation processes underlie the production of strong alcoholic beverages. The beneficial physiological properties of yeast allow them to be used in biotechnology. Currently, they are used in the production of xylitol, enzymes, food additives, and for cleaning oil contaminants.

Yeast is also widely used in science as a model organism for genetic research and in molecular biology. Baker's yeast was the first eukaryote to have its genomic DNA sequence completely determined. An important area of ​​research is the study of prions in yeast.

Traditional processes

Bakery

Main article: Bakery

Granulated dry active yeast - commercial product for baking

Making baked yeast bread is one of the oldest technologies. This process mainly uses Saccharomyces cerevisiae. They carry out alcoholic fermentation with the formation of many secondary metabolites, which determine the taste and aromatic qualities of bread. The alcohol evaporates during baking. In addition, bubbles of carbon dioxide form in the dough, causing it to “rise” and after baking, giving the bread a spongy structure and softness. A similar effect is caused by adding soda and acid (usually citric acid) to the dough, but in this case no flavor compounds are formed.

Flour is usually low in fermentable sugars, so eggs or sugar are added to the dough. To extract more flavor compounds, the dough is pierced or kneaded, releasing carbon dioxide, and then left to “rise” again. However, there is a risk that the yeast will not have enough fermentable substrate.

Winemaking

Grapes with a layer of yeast on them.

Yeast is naturally present on the surface of grape fruits; they are often noticeable as a light coating on the berries, formed mainly Hanseniaspora uvarum. Although "wild" epiphytic yeasts can produce unpredictable fermentation results, they usually cannot compete with wine barrel fermenters.

The collected grapes are pressed to obtain juice (must, grape must) with 10-25% sugar. To obtain white wines, a mixture of seeds and peels (pulp) is separated from it; it remains in the must for red wines. Fermentation then converts the sugars into ethanol. Secondary metabolites of yeast, as well as compounds obtained from them during wine maturation, determine its aroma and taste. To obtain a number of wines (for example, champagne), already fermented wine is fermented a second time.

The cessation of fermentation is associated either with the depletion of sugar reserves (dry wine) or with the achievement of the ethanol toxicity threshold for yeast. Sherry yeast, unlike regular yeast (which dies when the alcohol concentration in the solution reaches 12%), is more stable. Initially, sherry yeast was known only in the south of Spain (in Andalusia), where, thanks to its properties, strong wine was produced - sherry (up to 24% with long aging). Over time, sherry yeast was also discovered in Armenia, Georgia, Crimea, etc. Sherry yeast is also used in the production of some strong beers.

Brewing and kvass making

Barley malt

In brewing, grain (most often barley) is used as a raw material, containing a lot of starch, but little sugar fermentable by yeast. Therefore, starch is hydrolyzed before fermentation. For this purpose, amylases are used, formed by the grain itself during germination. Sprouted barley is called malt. The malt is ground, mixed with water and boiled to produce wort, which is subsequently fermented with yeast. There are bottom-fermenting and top-fermenting brewer's yeasts (this classification was introduced by the Dane Christian Hansen).

Top-fermenting yeast (for example, Saccharomyces cerevisiae) form a “cap” on the surface of the wort, prefer temperatures of 14-25°C (therefore, top fermentation is also called warm) and can withstand higher alcohol concentrations. Bottom (cold) fermentation yeast ( Saccharomyces uvarum, Saccharomyces carlsbergensis) have an optimum development at 6-10°C and settle to the bottom of the fermenter.

Use of yeast in modern biotechnology

Industrial alcohol production

Alcoholic fermentation is a process leading to the formation of ethanol (CH 3 CH 2 OH) from aqueous solutions of carbohydrates (sugars), under the action of certain types of yeast (see fermentation) as a type of metabolism.

In biotechnology, sugar cane, feed corn and other cheap sources of carbohydrates are used to produce alcohol. To obtain fermentable mono- and oligosaccharides, they are destroyed by sulfuric acid or amylases of fungal origin. Then fermentation and rectification distillation of the alcohol is carried out to a standard concentration of about 96% vol. . Yeast genus Saccharomyces were genetically modified to ferment xylose, one of the main monomers of hemicellulose, which makes it possible to increase the yield of ethanol when using plant raw materials containing, along with cellulose, significant amounts of hemicelluloses. All this can reduce the price and improve its position in the competition with hydrocarbon fuels.

Nutritional and feed yeast

However, in the 1990s, due to hygienic and environmental problems in the production and use of microbial protein, as well as the economic crisis, production decreased sharply. Accumulated data indicated the manifestation of a number of negative effects of the use of paprin in fattening poultry and animals. For environmental and hygienic reasons, interest in this industry has decreased throughout the world.

Nevertheless, in the West various yeast extracts are now produced and sold: vegemite, marmite, Bovril, Tsenovis. There are similar production facilities in Russia, but their volumes are small. To obtain extracts, either yeast autolysates are used (the cells are destroyed and the protein becomes available thanks to the enzymes of the cells themselves), or their hydrolysates (destruction by special substances). They are used as food additives and to add flavor to dishes; In addition, there are cosmetics based on yeast extracts.

Also sold are deactivated (killed by heat treatment) but not destroyed nutritional yeast, which is especially popular among vegans due to its high protein and vitamin content (especially group B), as well as low fat content. Some of them are enriched with vitamin B 12 of bacterial origin.

Yeast is a fungus whose cells are microscopic in size (about 5 microns) and bud, forming something like colonies. Yeast usually does not form mycelium. The shape of yeast cells is spherical.

In nature, yeast lives on the surfaces of fruits and flowers, they are present in the surface layers of the soil, the digestive tract of some insects, etc.

Yeasts are not a single taxonomic group of fungi. Yeasts include individual representatives of two divisions of fungi - ascomycetes and basidiomycetes. Yeast can be considered a special life form that arose from different types of fungi. There are more than 1000 types of yeast.

Yeasts are considered secondary unicellular organisms. This means that their ancestors were multicellular forms of fungi, which later became unicellular. Currently, there are peculiar “transitional” forms. Thus, some fungi at some stages of the life cycle have characteristics of yeast, and at others they form multicellular mycelium.

Budding is essentially the vegetative propagation of yeast, i.e. the formation of spores. A bulge forms on the parent cell, which gradually grows, turns into an adult cell and can be separated from the parent cell. When the cells bud, the yeast looks like branching chains.

In addition to vegetative reproduction, yeast undergoes a sexual process when two yeast cells fuse to form a diploid cell, which subsequently divides to form haploid spores.

Ascomycete yeasts differ from basidiomycete yeasts in their life cycle, synthesized substances, budding characteristics, etc.

Nutrition of yeast cells is mainly carried out by fermentation of low molecular weight carbohydrates (sugars). Sugars are fermented by yeast into alcohol and carbon dioxide. In this case, energy is released that goes into the vital processes of yeast.

Fermentation is anaerobic respiration, i.e. obtaining energy without oxygen. However, yeast can also breathe oxygen. Thus, their anaerobicity is facultative (optional). When yeast breathes oxygen, it releases carbon dioxide, but does not ferment sugars into alcohols. However, if there is a lot of sugar, then the yeast will ferment it even in the presence of oxygen.

The process of yeast fermentation is used by humans. In bread baking, carbon dioxide produced by yeast makes the dough more porous. The production of alcohol by yeast is used in winemaking and brewing. Also, during its metabolism, yeast produces other substances (various oils, alcohols, etc.), which give finished food products a special taste.

Man learned to use yeast back in ancient times. Their use was noted in ancient Egypt. However, people did not know then that these microscopic fungi ensure the rise of dough or the formation of alcohol. Yeast was first observed by A. Leeuwenhoek (in 1680), then it was described by Charles Cagniard de La Tour (1838). However, only in 1857 L. Pasteur finally proved that fermentation in raw foods is provided by organisms, and this is not just a chemical reaction.

Some types of yeast can cause illness.

Yeast belongs to the group of unicellular fungi that have lost their mycelial structure, because their habitats have become liquid or semi-liquid substrates containing large quantities of organic substances. The group of yeast fungi includes 1,500 species that belong to the classes Basidiomycetes and Ascomycetes.

In nature, yeasts are widespread and live on substrates rich in sugars, feeding on flower nectar, plant juices, dead phytomass, etc. Yeasts can live in soil and water, and in the intestines of animals.

Yeasts are fungi that live for all or most of their life cycle in the form of individual, single cells. The size of yeast cells averages from 3 to 7 microns in diameter, but there are some species whose cells can reach 40 microns. Yeast cells are nonmotile and oval in shape. Although yeasts do not form mycelium, they exhibit all the signs and properties of mushrooms. Yeasts are organotrophic eukaryotes with an absorption type of nutrition. These fungi use organic substances to obtain carbon and energy necessary for life. For respiration, yeast needs oxygen, but in the absence of oxygen, many types of facultative anaerobes of yeast fungi obtain energy as a result of fermentation with the formation of alcohols. Yeast fermentation stops or stops altogether if oxygen begins to flow to the fermenting substrate, since respiration is a more efficient process for obtaining energy. But if the concentration of sugars in the nutrient medium is very high, then even with access to oxygen, the processes of respiration and fermentation occur simultaneously. Yeast fungi are very demanding regarding nutritional conditions. In an anaerobic environment, yeast metabolizes only glucose, while in an aerobic environment they can also use hydrocarbons, fats, aromatic compounds, organic acids, and alcohols as energy sources.

Yeast grows and multiplies at tremendous speed, causing characteristic changes in the environment. Thus, thanks to the process of alcoholic fermentation, yeast has become widespread throughout the world. Yeast is believed to be the oldest plant cultivated by humans.

Yeast propagation is carried out by budding (division). Sexual reproduction is also possible. In this case, the resulting zygote is transformed into a “bag”, which contains 4-8 spores. In the unicellular state, yeast is capable of vegetative reproduction. Thus, spores or zygotes can bud. The division of yeasts into groups (classes Ascomycetes or Basidiomycetes) is based on their methods of sexual reproduction. There are species of yeast that do not reproduce sexually. Scientists included them in the class of imperfect mushrooms (Fungi Imperfecti, or Deuteromycetes).

Since ancient times, certain types of yeast have been used by humans in the production of wine, beer, bread, kvass, in the industrial production of alcohol, etc. Some types of yeast are used in biotechnology due to their important physiological properties. In modern production, using yeast, food additives, enzymes, xylitol are obtained, and water is purified from oil contamination. But there are also negative properties of yeast. Some types of yeast can cause diseases in humans because they are facultative, or opportunistic, pathogenic microorganisms. Such diseases include candidiasis, cryptococcosis, and pityriasis.

The kingdom of mushrooms is one of the most unusual and impressive in the world of wildlife. The diversity of these organisms is truly impressive, and their properties are worthy of careful study. People encounter some of their species every day, without even thinking that they are mushrooms. It is these varieties that are worth dwelling on in more detail.

What types of mushrooms are there?

This kingdom has a complex classification. Most people understand mushrooms as only one type, the main one is cap mushroom. It includes both edible and poisonous options - champignons, truffles, boletus, chanterelles, fly agarics, toadstools and many others.

Another, even more interesting species are molds. They are distinguished by their microscopic sizes, due to which the fruiting bodies and mycelium are almost impossible to notice with the naked eye. But in general, it’s not at all difficult to see them - just leave a piece of bread in a damp place, and soon the familiar fluffy coating will appear on it. These are molds, namely saprophytes, an inedible species that often spreads over fruits, vegetables, soil and the walls of damp, dark rooms.

The third type is yeast. They have been known to man for a long time and are as widespread as molds. For example, it is to them that people owe the existence of bread, beer, wine and kvass. Molds and yeasts reproduce equally well in everyday human environments, but, unlike the former, which prefer dampness and twilight, the latter need sugar. But there is one thing in common - yeast is also impossible to examine in detail without a microscope. Today, people know about 1,500 of their varieties.

Yeast mushrooms

This species differs from all others in that it has lost the mycelial structure classic for the kingdom. Yeast lives in a liquid or semi-liquid environment filled with organic matter. They exist in the form of dividing or budding cells. This structure allows them to have the highest possible metabolic rate, so they can grow and reproduce quickly. Although molds and yeasts appear similar due to their microscopic size, the former still have mycelium and all the characteristic features, while the latter constitute a single cell. The history of the origin of the name of this variety is interesting. The word "yeast" refers to the shaking that can be seen in fermented wort or rising dough.

Features of molds

This variety retains most of the properties of the cap species. However, they differ in microscopic size. Molds form the finest branched mycelium, from which large fruiting bodies do not separate. They were the first inhabitants of planet Earth, where they appeared more than two hundred million years ago. The mycelium of a mold fungus develops in almost all conditions in nature, regardless of the availability of food and the characteristics of the habitat. Huge colonies appear instantly in the presence of humidity and a sufficiently high temperature.

The types of mold fungi are very numerous, but they have common features - the mycelium serves as the basis, and thin branching threads are located directly inside the affected surface. Unlike yeast, they reproduce sexually or vegetatively. The cell of a mold fungus does not make up its entire body. However, this does not prevent them from spreading with great speed.

The most famous molds

Some of the kingdom's representatives are more important to humanity than others. These are penicillium molds, which are green spots that grow on plant substrates and ordinary foods. They produce an antibiotic called penicillin, which was the world's first antibacterial drug. His invention changed the world of medicine. Both molds and bacteria can be harmful to human health. But a variety called penicillium can save lives, which is why it has earned its widest fame.

Class Phycomycetes

One of the most common species is Phycomycetes, or mucor molds. There are more than three hundred varieties in this family. The three most common are: Mucor, Thamnidium and Rhizopus. The structure of mucor molds is different in that their mycelium often consists of a single branched cell. Ball-shaped hyphae filled with many spores extend from it. The spread of mucoraceae occurs easily and quickly on many types of substrate, with the exception of dairy products, and stops only at temperatures below -8 degrees Celsius.

Class Ascomycetes

It is this family that includes penicillium fungi, as well as some others, for example, the genus Aspergillus. Otherwise, this class is called marsupials. While mucor molds form primitive unicellular mycelium, ascomycetes have a more complex structure that quickly forms separate colonies that grow over the substrate. Spores immediately form on it, to which the mold owes its fluffy grayish-green appearance. When examined under a microscope, the reasons for the name become obvious - the structure of molds includes long chains of conidia containing spores, which form a brush or bag. Ideal conditions for development are dampness and poor ventilation at temperatures close to 0 degrees Celsius.

Difference between Aspergillus and Penicillum

Being in the same family, these molds are similar in appearance. They have a colorless mycelium with colored spherical conidia; as a rule, they are distinguished by a grayish-blue or gray-green tint, less often with a yellow tint. However, the role of the aspergillus mold is markedly different. While penicillin is an important component of medicines, the penicillin-related species contains substances that cause spoilage in dairy or meat products.

Imperfect mushrooms

This class has not been studied as widely as those described above. Imperfect species of mold fungi reproduce in a way different from sexual, unknown in detail. They are distinguished by septate mycelium with cluster-shaped spores of dark color. Because of this, infection with such fungi forms black velvety spots. This type of mold develops well at low temperatures and has a large affected area - when it appears on meat, it penetrates deep into the muscle tissue. It is these fungi that can lead to internal mold and spoil butter, cheese, and egg products.

Milk mold

Mushrooms of the Oidium lactis variety resemble yeast in their structure. They have white septate mycelium with separated spores in the form of single cells. The diet of molds of this type includes a variety of dairy products. Their appearance appears in the form of a fluffy white coating that can cover the surface of sour cream, yogurt or cottage cheese. Mold reduces their acidity, causing the product to spoil. Some scientists classify them as yeasts due to the simplicity of their cell chains and felt-like mycelium.

Mold that grows in the refrigerator

Several types of fungi can attack foods that are stored at sufficiently low temperatures. First of all, this is Botrytis, characterized by creeping mycelium of a felt-like appearance, with colorless conidia appearing in bunches. Molds also include those that are distinguished by brown or olive conidiophores. A similar species develops in the refrigerator at temperatures below 5 degrees Celsius and affects a variety of foods. Another dangerous species to eat is Alternaria. These include mushrooms with pear-shaped or pointed conidia of brown or olive color. This mold can affect not only chilled but also frozen meat, as well as butter and other food products.

Thomas class

These molds differ from all others in their original structure. They do not form external mycelium and most often develop inside the substrate undergoing the process of decay. To reproduce, Phoma molds use short conidiophores with intertwined hyphae surrounding them like a shell.

How does mold affect the human body?

Not all types of mushrooms are as beneficial for humanity as penicillium mushrooms. More often the situation is quite the opposite, and the appearance of mold is a bad sign. First of all, its spores have a very negative effect on the mucous membranes of the body, causing immune reactions. This is one of the most powerful allergens, and people with certain problems in this area are guaranteed to experience discomfort at the slightest contact with mold. And it’s not just a short-term reaction - over time, everything can end in serious illness. In houses affected by mold fungi, eight out of ten residents develop asthma. The figure is quite impressive. And these are not all possible problems.

If such a problem arises, you need to think about ways to destroy mushrooms as soon as possible. To do this, you should use a special antiseptic, which can be purchased at a building materials store. It is necessary to work with it as carefully as possible, having studied the instructions for use. In addition, before starting to combat mold, it is worth examining how deeply the surface is affected. Sometimes it is better to throw away the contaminated item. If the defeat is not so large-scale, you can begin to take action. First of all, pay attention to the antiseptic primer. It will not only destroy mold, but also prevent its reappearance. Using this product is quite simple; most often you don’t even need to dilute it with water. It is only recommended to clean the surface before treatment.

If there is no opportunity or desire to look for a special remedy, you should turn to home methods. For example, bleach may be a great option. The sodium hypochlorite it contains kills not only mold, but also its spores. Bleach is ideal for cleaning bathroom tiles, floors, or glass. But for other items it can be dangerous - many things lose color or deteriorate from such treatment. In addition, bleach is quite toxic, so you should only use it in a well-ventilated room, armed with protective rubber gloves.

Vinegar is less dangerous in such cases. It is not that toxic, so it can be used without fear. You should use vinegar using a spray bottle or by soaking a rag in it and wiping the mold-affected surface.

For those who do not have such a remedy in their arsenal, hydrogen peroxide is suitable. It can be bought at any pharmacy, it is not hazardous to health and does not have a pungent odor. Peroxide can be used to combat mold on a variety of surfaces, but you must be aware of its bleaching effect, which can be harmful to fabrics or paints.

For hard surfaces like tiles and glass, ammonia will also work. It is enough to mix it with water in equal proportions and spray the mixture over the entire infected area, and after a few hours, rinse it with water.

The safest solution is baking soda. It will not harm any family members or pets. To combat mold, a teaspoon of baking soda is dissolved in a glass of water, after which the mixture can be sprayed on the affected surfaces. It is not necessary to wash off the solution - it will be a preventive measure.