Mucor penicillium aspergillus. Order Eurotiales (And
One way or another, everyone is familiar with mushrooms. There are many fans of “quiet hunting” among us, who appreciate leisurely walks through the forest, relieving the stress of city life. Collected mushrooms are used to prepare a variety of delicious dishes that invariably decorate friendly feasts, and when dried, salted or pickled, they are stored for a long time. But few people know how vast the kingdom of mushrooms is and how closely our lives are connected with it. We will talk about this in our articles.
The meaning of mushrooms
In everyday life, only the fruiting bodies of cap mushrooms are called mushrooms, and few people remember that the world of mushrooms includes a huge number of other species of organisms.
Currently, there are up to 100 thousand species of mushrooms. Mushrooms are very diverse in size, appearance and other characteristics. In different states and phases of their development, they are present everywhere: in soil, air, water, inside other living organisms and on their surface. The role of mushrooms in our diet is much more varied than most people suspect, and, unfortunately, it is not always beneficial.
Fungi are heterotrophic organisms and require ready-made organic substances for their existence. Enzymes secreted by fungi act on the substrate and contribute to its partial digestion outside the fungal cell. Such semi-digested material is easily absorbed by the entire surface of the cell.
The role of mushrooms in the cycle of substances in nature is great. As decomposers, i.e. Destroyers of organic matter, they mineralize organic matter, making carbon dioxide, nitrogen compounds, phosphorus, potassium and other elements of mineral nutrition again available for use by other organisms. Therefore, saprophytic fungi, which destroy dead organic matter, constitute an important element of diverse plant communities.
However, in addition to mushrooms that are content with forest litter and other plant debris, there are many whose activities cause significant harm. Some of them like our food supplies - they spoil them, and sometimes make them poisonous. Fungi destroy wooden buildings and many materials and products made from them. For example, fungi can spoil fabrics, leather, paper, cardboard, paints and varnishes, damaging books and paintings, and sometimes causing irreparable damage to libraries and museums. The list of materials affected by fungi includes lubricating oils and other petroleum products, cable and wire insulation, wax, and photographic film. There are types of fungi that can settle on metal products and lenses of optical instruments, damaging them in the process of their life activity. The damage caused by mushrooms is especially great in humid and warm climates. For example, during the Second World War, less than 50% of military cargo sent to the tropics and subtropics arrived there usable without additional repair work.
It has long been noticed that many mushrooms in the forest grow near certain trees - this is reflected in their names: boletus, boletus, etc. This choice of habitat is due to the fact that they closely cooperate with higher plants, forming mycorrhiza (“fungal root”) with their roots. On the other hand, seedlings of many species of forest trees grow poorly and even die if the soil does not contain the mycorrhiza-forming fungi they need. By forming mycorrhiza with plants, fungi supply the plants with mineral nutrition elements, primarily phosphorus, the compounds of which are inaccessible in the soil. Plants, in turn, share the products of photosynthesis with fungi.
Mycorrhiza is characteristic of most higher plants. The orchid family shows a particularly strong attachment to mushrooms: symbiosis with fungi is mandatory for all species of this family - orchid seeds must be infected with the fungus during germination, otherwise the development of orchids stops. Until such a close connection between orchids and fungal flora was discovered, tropical species of orchids could not be introduced into greenhouse culture in Europe.
The biochemical properties of fungi are widely used, primarily yeast, which break down sugar to form ethyl alcohol and carbon dioxide. Alcoholic fermentation underlies a number of food industries - bakery, winemaking, brewing, as well as the production of technical alcohol from waste from the pulp and paper industry. Some types of fungi synthesize antibiotics, the first of which was penicillin. Fungi from the genera Penicillium and Aspergillus have found use in the production of not only antibiotics, but also some organic acids and enzymes. Transplant operations for the heart and other organs began to produce encouraging results in the early 1980s, when cyclosporine, isolated from a soil fungus, began to be used: this substance suppresses rejection reactions without producing the side effects characteristic of previously used drugs.
The structure and reproduction of mushrooms
In most fungi, the vegetative body is a mycelium (mycelium), consisting of thin, several microns thick, branching filaments-hyphae with apical growth and lateral branching. The mycelium penetrates the substrate and absorbs nutrients from it over its entire surface ( substrate mycelium). The mycelium can also be located on the surface of the substrate and rise above it ( surface and air mycelium) - then it can be seen with the naked eye or with a magnifying glass as a white or colored loose mesh, fluffy (sometimes cotton wool-like) coating or film. Reproductive organs are usually formed on aerial mycelium.
Distinguish noncellular mycelium, devoid of partitions and representing, as it were, one giant cell with a large number of nuclei, and cellular mycelium, divided by septa into individual cells containing one, two or many nuclei.
To be continued
3.1. Mushrooms (Fungi)
3.1.1. Basic properties and taxonomy of mushrooms
Fungi are eukaryotes that have lost chlorophyll, and therefore they are the same heterotrophs as animals. At the same time, they have a rigid cell wall and are not able to move, like plants. Due to established traditions, mushrooms have always been classified as plants *, but in more modern systems, for example, in the classification shown in Fig. 3.1, they are classified into a separate kingdom. The taxonomy and main characteristics of fungi are presented in Fig. 3.2 and in table. 3.2. The two largest and most highly organized groups are Ascomycota and Basidiomycota.
* (At one time, mushrooms received the status of a class and, together with the class of algae, constituted a phylum Thallophyta plant kingdom. TO Thallophyta included plants whose body could be called a thallus. Thallus- this is a thallus, most often flattened, not differentiated into true roots, stems and leaves and without a real conducting system.)
3.1. Make a table of the differences between fungi and chlorophyll-containing plant cells; using the information about the kingdom of mushrooms that is given in table. 3.2.
Structure
The body structure of mushrooms is unique. It consists of a mass of thin branching tubular filaments called hyphae(singular - hypha), and this whole mass of hyphae is called mycelium. Each hypha is surrounded by a thin, rigid wall, the main component of which is chitin, a nitrogen-containing polysaccharide. Chitin is also a structural component of the exoskeleton of arthropods (Section 5.2.4). In some cases, the cell wall contains cellulose. Hyphae do not have a cellular structure. The protoplasm of the hyphae is either not divided at all, or is separated by transverse partitions, which are called septa. Such septa divide the contents of the hyphae into separate compartments that look like cells. Unlike normal cell walls, the formation of septa is not associated with nuclear divisions. In the center of the septum, as a rule, there remains a small hole (pore), through which protoplasm can flow from one compartment to another. Each compartment may contain one, two, or several nuclei, which are located along the hypha at more or less equal distances from each other. Hyphae that do not have septa are called unarticulated (unseptated, aseptated) or coenocytic. The latter term is applied to any mass of protoplasm in which there are many nuclei, but which is not divided into individual cells. Hyphae that have septa are called articulated or septated. The cytoplasm of the hyphae contains mitochondria, the Golgi apparatus, the endoplasmic reticulum, ribosomes, vacuoles and other organelles common to eukaryotes. In older areas of mycelium, the vacuoles are larger, and the cytoplasm occupies only a small space at the periphery. From time to time, hyphae aggregate to form denser structures, such as the fruiting bodies of Basidiomycota.
Nutrition
Saprophytes. Saprophytic fungi produce a wide variety of enzymes. If the fungus is capable of secreting digestive enzymes of three main classes, namely carbohydrases, lipases and proteases, it can use a wide variety of substrates, and it can be called truly ubiquitous, for example, any of the Penicillium species, which forms green or blue mold on such substrates, like soil, raw leather, bread or rotting fruit.
The hyphae of saprophytic fungi are usually characterized by chemotropism, i.e. they grow in the direction where the substances diffusing from the substrate are located (Section 15.1.1).
Saprophytic fungi usually produce large numbers of light, resistant spores. This allows them to be easily extended to other products. Examples of such fungi are Misor, Penicillium or Agaricus.
Saprophytic fungi and bacteria together form a group of so-called decomposers, without which the cycles of elements in nature are unthinkable. Particularly important are the few fungi that secrete cellulase, an enzyme that breaks down cellulose. Cellulose is an essential structural component of plant cell walls. The rotting of wood and other plant debris is partly achieved through the activity of decomposers that secrete cellulase.
Some saprophytic fungi are of economic importance; These fungi include, for example, the yeasts Saccharomyces or Penicillium (Section 3.1.6).
If the host is a plant, the fungal hyphae penetrate through the stomata, or directly through the cuticle and epidermis, or through wounds. Once inside the plant, the hyphae typically branch, spreading between cells; sometimes they secrete pectinases, which digest the plant tissue, and thus make their way through the middle plate. The disease can be systemic, that is, it affects all tissues of the host, or it can be limited to a small part of the plant.
Symbiosis. Fungi are involved in the creation of two very important types of symbiotic unions, namely lichens and mycorrhizae. Lichen is a symbiotic association of fungus and algae. The fungus in this case is usually either marsupial or basidial, and the algae is either green or blue-green. Lichens typically live on exposed rocks or tree trunks; in damp forests they also hang from trees. It is believed that the algae supplies the fungus with organic products of photosynthesis, and the fungus absorbs water and mineral salts. In addition, the fungus stores water, which allows some lichens to grow in dry conditions where no other plants can survive.
The body of the lichen is small and does not resemble either partner, this union has gone so far. Lichens grow very slowly and are very sensitive to environmental pollution, especially sulfur dioxide, such a common industrial waste. Therefore, lichens are an ideal means for controlling environmental pollution, since their numbers and species diversity increase sharply with increasing distance from the source of pollution.
Mycorrhiza is a symbiotic association of a fungus with plant roots. Probably most terrestrial plants are capable of entering into this kind of relationship with soil fungi. The fungus forms a sheath around the central part of the root ( ectotrophic mycorrhiza) or penetrates the tissues of the host plant ( endotrophic mycorrhiza). Mycorrhiza of the first type is found mainly in forest trees such as conifers, beech and oak, and is formed with the participation of fungi belonging to the department Basidiomycota. Their "fruiting bodies" (what we call mushrooms) can usually be seen near trees. The fungus receives carbohydrates and vitamins from the tree and, in turn, breaks down the proteins of soil humus into amino acids; Some of the amino acids are absorbed and used by the tree. In addition, the fungus provides the tree with a larger absorption surface, which is especially important when the tree grows in poor soil lacking nitrogen.
Endotrophic mycorrhiza occurs in a wide variety of plants, but very little is known about its role in symbiosis.
3.1.2. Division Oomycota
Obvious signs of rot on the leaves usually appear in August, although, as a rule, infection occurs in the spring, when the fungus penetrates the leaves of plants grown from tubers in which the mycelium has overwintered.
The mycelium, consisting of branched unsegmented hyphae, branches in the intercellular space inside the leaves, forming branched haustoria, which penetrate the mesophyll cells and suck nutrients from them (Fig. 3.3 and 3.4). With excess moisture and heat, long thin structures appear on the mycelium, which are called sporangiophores. Sporangiophores, penetrating through stomata or wounds, hang from the lower surface of the leaves. They branch and give rise sporangia(Fig. 3.4). In warm weather, sporangia behave like spores, that is, they are carried by the wind or along with splashes from raindrops to other plants, thus spreading the infection. Then a hypha grows from the sporangium, which penetrates through stomata, lentils or damage into the plant tissue. In cold conditions, the contents of the sporangium divide to form motile zoospores (this feature is characteristic of primitive organisms), which are released from the sporangium and float in a thin layer of liquid adsorbed on the surface of the leaf. Zoospores can encyst and wait in this state until conditions become more favorable for hyphal growth; then a new infection of plants begins.
In diseased plants, small dead (“rotten”) brown areas are visible on individual leaves. If you look closely, you can see a fringe of white sporangiophores on the undersurface of infected leaves around the dead zone. In warm, damp weather, zones of necrosis quickly spread over the entire surface of the leaf and spread to the stem. Some sporangia fall to the ground and infect potato tubers, and the infection spreads very quickly and causes a kind of dry rot, in which the tuber tissue becomes rusty brown in color, spreading unevenly from the periphery to the center of the tuber.
Phytophthora usually overwinters as dormant mycelium inside slightly infected potato tubers. It is believed that, unlike Peronospora, this fungus rarely reproduces sexually, unless, of course, we talk about those places (Mexico, Central and South America) where potatoes originated. Sexual reproduction of the fungus can be induced in the laboratory. Like Peronospora, Phytophthora produces stable, resting spores. A thick-walled oospore is formed as a result of the fusion of an antheridium and oogonia. It can overwinter in the soil and cause a new infection the following year.
In the past, epidemics * caused by Phytophthora have led to very serious consequences. It is believed that this disease was accidentally brought to Europe from America in the late 1930s. As a result, a whole war of epiphytoties swept across Europe, which in 1845 and subsequent years completely destroyed potato crops in Ireland. Famine ensued, which led to the death of many people, victims not only of the potato disease itself, but also of complex political and economic factors. As a result, many Irish families were forced to emigrate to North America.
* (Mass plant diseases are called epiphytoties. - Approx. translation)
This fungus is also interesting for us because in 1845 Berkeley was the first to clearly show the microbial nature of late blight. Berkeley demonstrated that the fungus associated with potato blight caused the disease itself rather than being a byproduct of decomposition.
Understanding the life cycle of the potato rot pathogen has led to the development of methods to combat this disease. These methods are listed below.
1. Care must be taken to ensure that not a single infected tuber is planted.
2. Since the fungus can persist in the soil for almost a whole year, you should not plant potatoes where this disease was discovered last year. In this case, correct crop rotation helps.
3. All diseased parts of infected plants should be destroyed before digging up the tubers, for example by burning them or spraying them with a caustic solution such as sulfuric acid. This must be done because rotten tops (i.e. stems) and above-ground parts can also infect tubers.
4. Since this fungus can overwinter in undug tubers, you need to carefully ensure that all tubers in infected fields are dug up.
5. The mushroom can be treated with copper-containing fungicides, such as Bordeaux mixture. Spraying should be carried out at a strictly defined time in order to have time to prevent the disease, since nothing can save the affected plants. Plants are usually sprayed every two weeks, from the moment they grow a few centimeters until the tubers are fully ripe. Selected "seed" potatoes can be sterilized externally by immersing the tubers in a dilute solution of mercuric(II) chloride.
6. Constant monitoring of meteorological conditions and early warning to farmers can help determine when to spray crops.
7. At one time, selection was carried out for potato resistance to rot. As is known, wild potato Solanum demissum is highly resistant to late blight, so it was used in breeding experiments. The biggest obstacle to obtaining the necessary immunity is that there are many strains of the fungus, so so far it has not been possible to develop a single potato variety that is resistant to all of these strains. As new potato varieties are introduced into cultivation, new strains of fungi appear. This problem has long been familiar to plant pathologists; it once again reminds us of the need to preserve the gene pool of the wild ancestors of our modern crops as a source of genes for resistance to various diseases.
3.1.3. Division Zygomycota
The main characters of Zygomycota are given in Table. 3.2. Like Oomycota, this is a small group of fungi, which is generally considered to be less highly organized than the two main divisions Ascomycota and Basidiomycota.
Let's take Rhizopus as an example. This is an ordinary saprophyte, similar in appearance and structure to Misor, but much more widespread. Both Rhizopus and Misor are called capitate molds for a reason that you will learn about later (see features of asexual reproduction). One of the most common species of Rhizopus stolonifer is the common bread mold. It also grows on apples and other fruits, causing soft rot in storage.
Structure
The structure of the mycelium and individual hyphae is shown in Fig. 3.5. The mycelium branches abundantly and does not have septa. Unlike Miso, such mycelium forms aerial stolons, which bend in an arc over the surface of the medium, touch it again and form hyphae, which are called rhizoids. Sporangiophores develop at these points.
Rice. 3.5. A. Microphotograph of part of the Mucor hiemalis mycelium obtained using a scanning electron microscope. Sporangia are clearly visible, × 85
Life cycle
The life cycle of Rhizopus stolonifer is schematically presented in Fig. 3.6.
Asexual reproduction
After two to three days of cultivation, Rhizopus forms vertically growing hyphae called sporangiophores. They have negative geotropism. The tip of each sporangiophorus swells and turns into sporangium. The sporangium is separated (Fig. 3.7) from the sporangiophorus by a convex transverse septum, which is called column. The protoplasm of the sporangium is divided into parts, then its own cell wall appears around each such part and a spore containing several nuclei is formed. In appearance, sporangiophores and sporangia resemble a pad studded with pins. Therefore, Rhizopus and other mushrooms close to it, for example Misor, are called capitate molds or black mold. As the sporangium matures, it turns black and dries out; eventually the wall of the sporangium bursts and a mass of dry, small, dust-like spores spills out. The column is flattened, as can be seen in Fig. 3.7, and you get a wide launch pad from which spores can easily be blown away and scattered. In rainy weather, sporangia do not dry out or crack, which prevents the release of spores in unfavorable conditions. Once on a suitable substrate, the haploid spores germinate and a new mycelium is formed.
3.2. What are sporangiophores needed for?
Sexual reproduction
Many fungi exist as two strains that differ in their behavior during sexual reproduction. Sexual reproduction is only possible between different strains, even if both strains produce both male and female reproductive organs. Such autosterile mushrooms are called heterothallic, and such strains are usually designated as (+) - and (-) - strains (in no case should they be called male and female). The strains do not differ from each other in structure; there are only slight physiological differences between them. Fungi that have only one such strain and are therefore autofertile are called homothallic. The advantage of heterothallism is cross-fertilization, which allows for greater variability to occur.
Rhizopus stolonifer is a heterothallic mushroom. All stages of sexual reproduction are schematically depicted in Fig. 3.8. Initial events are caused by the diffusion of hormones from strain to strain. Such hormones stimulate the growth of long hyphae connecting individual colonies. These hyphae apparently secrete some kind of volatile chemicals that serve as a signal to attract a strain of the opposite “sex,” i.e., a kind of chemotropism is observed.
Typical gametes are not formed, and fertilization is reduced to pairwise fusion of nuclei, as shown in Fig. 3.8. Since gametangia do not differ from each other in size, this process of sexual reproduction is called isogamy.
After the fusion of the nuclei, a zygospore is formed, which contains many diploid nuclei. All but one of these nuclei are believed to degenerate. The remaining nucleus undergoes meiotic division to form four haploid nuclei, of which only one is again retained. Whether it will be a (+) - or (-) - strain is a matter of chance.
Unlike spores produced by asexual reproduction, zygospore is not intended for dispersal, but for a kind of “hibernation”; For this, it has both a supply of nutrients and a thick protective wall. Dispersal occurs immediately after germination of the zygospore, when, as shown in Fig. 3.8, sporangia are formed and asexual reproduction begins. During germination, the remaining haploid nucleus divides mitotically; As a result of repeated divisions, a large number of haploid nuclei are formed, with each of them giving rise to one of the spores in the sporangium. Therefore, all these spores belong to the same strain. All stages of sexual reproduction are schematically presented in Fig. 3.6.
3.1.4. Division Ascomycota
The main characters of Ascomycota are given in Table. 3.2. This is the most numerous and relatively highly organized group of fungi, which is distinguished by greater structural complexity than that of Zygomycota, especially in the structure of the reproductive organs. The Ascomycota include yeasts, a number of common molds, true mealy fungi, fruit fungi, morels and truffles.
Penicillium is a widespread saprophyte; it forms blue, green, and sometimes yellow mold on a wide variety of substrates. Asexual reproduction of penicillium is carried out using conidium. Conidia are spores that form at the end of special hyphae called conidiophores. Conidia are not enclosed in sporangia; on the contrary, they are bare and disperse freely as they mature. The structure of Penicillium is shown in Fig. 3.9, A. The mycelium of this fungus forms small round colonies, and spores give the colonies a specific color, therefore the youngest outer edge of the colony is usually white, and the more mature central part of the mycelium, where spores form, is colored. We will discuss the economic importance of various Penicillium species in section. 3.1.6.
Aspergillus usually grows on the same substrates as Penicillium and is very similar to it. This fungus produces black, brown, yellow and green molds. For comparison with Penicillium in Fig. 3.9, B shows mycelium reproducing asexually.
Rice. 3.9. Asexual reproduction in two typical representatives of Ascomycota. A. Penicillium; The conidiophore has the appearance of a microscopic brush. B. Aspergillus (the conidiophore, spherically swollen at the apex, carries radially diverging chains of conidia). B. Scanning electron micrograph of the conidiophore Aspergillus niger. × 1372
* (The English terms "mushrooms" and "toadstools" are actually synonymous, although sometimes edible mushrooms are called mushrooms, and poisonous ones are called toadstools.)
Agaricus (Psalliota) belongs to the group of inedible cap mushrooms. What we call a "toadstool" or "mushroom" is actually a short-lived "fruiting body". The cap mushroom mycelium grows saprophytically on organic soil material and can live there for many years. It forms thick threads called rhizomorphs. The hyphae in these threads are collected very tightly, so that a kind of tissue is formed. Under unfavorable conditions, rhizomorphs go into a dormant state and remain in this state until good weather returns. They grow due to elongation of the apex and provide vegetative growth of the mycelium. The characteristic appearance of Agaricus is shown in Fig. 3.10, which also shows the structure of the plates.
In temperate latitudes, "fruiting bodies", or sporophores, appear in autumn; they consist entirely of hyphae, which are arranged very tightly, forming a kind of tissue. The edges of the plates consist of basidia, from which spores are formed ( basidiospores). The plates have positive geotropism and therefore hang down strictly vertically. Spores, of which a lot are produced (in a large mushroom, about half a million spores per minute), are forcefully ejected from the basidia, fall vertically down between the plates and are carried away by air currents.
3.1.6. Economic importance of mushrooms
Healthy mushrooms
Mushrooms and soil fertility. Saprophytic fungi play an important role in the cycles of nutrients. Together with saprophytic bacteria they form a group decomposers, decomposing organic material (Fig. 9.31 and Section 2.3.1).
Cleaning of drains(see also section 2.3.2). Saprophytic fungi, together with protozoa and saprophytic bacteria, are part of that jelly-like film of living things that covers the “filter loading” stones in wastewater treatment plants.
Fermentation production(see also section 2.3.4). The oldest fermentation industry is brewing. Beer is made from barley, which is first germinated slightly to convert the starch stored in the seeds into maltose sugar. To speed up this process and strictly control it, gibberellins are used (section 15.2.6). Further fermentation is carried out in large vats, where single-celled fungi “work” - yeast from the genus Saccharomyces (for example, S. cerevisiae or S. carlsbergensis). At this stage, sugar is converted into carbon dioxide and alcohol, the final concentration of which reaches 4-8%. At an early stage of fermentation, hops are added, which gives the beer aroma and suppresses the development of other microorganisms.
Winemaking is based on the fermentation of grape juice with wild yeast found on the skins of the berries. The final alcohol concentration reaches 8-15%, and this is quite enough to kill the yeast. After this, the wine is aged (though not always) for several years to mature. This leaves some unused sugar.
Other common fermented drinks include cider, made from apple juice, and Japanese sake, made from rice.
Industrial alcohol can be obtained from fermentation by-products, such as molasses, which contains a lot of sugar.
Another important branch of fermentation production, where yeast is also used, is baking. Bakeries use special strains of yeast that produce a lot of carbon dioxide, which helps the dough rise. Alcohol is also formed at the same time, but it evaporates during baking of bread. Another product that is still obtained from mushrooms is citric acid (2-hydroxypropane - 1,2,3-tricarboxylic acid), widely used in the food and pharmaceutical industries. It is formed by the fungus Aspergillus niger.
Both bacteria and fungi are used simultaneously in cheese making (Section 2.3.4). Some famous varieties of cheese are ripened thanks to the "work" of various species of Penicillium: these are Roquefort (P. roqueforti), Camembert (P. camemberti), Danish blue cheese and Italian Gorgonzola.
Antibiotics(see also section 2.3.5). The first antibiotic to be used in clinical practice was penicillin. It is formed by some species of Penicillium, in particular P. notatum and P. chrysogepit. Moreover, the latter species still serves as a source for the industrial production of this antibiotic. When penicillin began to be used in the early 40s, it seemed that its possibilities were limitless, since this antibiotic was active against all staphylococcal infections and a wide variety of gram-positive bacteria; In addition, it turned out to be practically non-toxic to humans. Until now, penicillin remains the most important antibiotic, and more and more new, more effective synthetic derivatives are constantly being introduced into medical practice, the starting raw material for which is still natural penicillin, obtained in large quantities from the industrial culture of this fungus. We have already discussed how penicillin works in section. 2.2.2.
Griseofulvin is another antibiotic that is obtained from Penicillium (especially P. griseofulvum). It has antifungal properties and is particularly effective (when administered orally) against fungal foot infections and ringworm. Fumagillin is a special type of antibiotic that is obtained from Aspergillus fumigatus. It is often used for amoebic dysentery.
Genetics. Some fungi have proven extremely useful for genetic research; this is primarily Neurospora (section 22.5.1). In the future, yeast may also be used for genetic engineering.
New food sources. In Sect. 2.3.6 we have already said that the protein of unicellular organisms is used for food. One such example is the continuous culture of Candida yeast on petroleum hydrocarbons, which was started in 1971 by British Petroleum at Grangemouth in Scotland. By the mid-70s, this crop produced 4,000 tons of protein concentrate per year, which was used as animal feed.
Mushrooms harmful to humans
Spoilage of food and materials. Saprophytic fungi play a very important role in the biosphere, but they cause quite a lot of trouble for humans, destroying many organic materials. Therefore, when storing grains, fruits and other products, it is necessary to apply a variety of protective measures. Food spoilage is a constant problem facing humanity. Natural fabrics, leather and other consumer goods made from natural raw materials are also destroyed by fungi. For example, fungi living on cellulose cause rot of various wood products and fabrics. A lot of money is spent on preserving all these materials.
1) (Sclerotia (singular - sclerotium) are stable, resting bodies with a hard wall, which are formed in some fungi, often as an adaptation for wintering.)
Fungi infect a variety of plant organs: potato cancer - underground parts; rust, true and downy mildew and black spot - leaves; smut and ergot - flowers; soft rot and mold - ripe fruits.
3.1.7. Practical lessons
When working with fungi, in many cases the same techniques are used as for working with bacteria, i.e. standard microbiological techniques. Many saprophytic fungi, like bacteria, can be grown on nutrient agar, and if a pure culture of fungi is needed, you should use the techniques for working under sterile conditions described in section. 2.7.2. Mucor, Rhizopus, Penicillium and Aspergillus are quite suitable for ordinary culture, and 2% malt agar poured into Petri dishes is best suited for media. The mushroom you choose can be isolated from a mixed culture that has grown on its own on bread, fruit or other juicy foods. The spores are transferred into the culture medium with a sterile syringe. The culture is best viewed under a stereoscopic microscope at low magnification.
Fungi are heterotrophs, i.e. they need an organic carbon source. In addition, they also require sources of nitrogen (usually organic, such as amino acids), inorganic ions (such as K + and Mg 2+ ), trace elements (such as Fe, Zn and Cu) and organic growth factors (such as vitamins). Different mushrooms require a strictly defined set of nutrients, so the substrates on which these mushrooms can be found are also different. Nutrition in fungi occurs by absorbing nutrients directly from the environment - unlike animals, which, as a rule, first swallow food and then digest it inside the body; Only after this does the absorption of nutrients occur. If necessary, mushrooms are capable of external digestion of food. In this case, enzymes are released from the body of the fungus onto the food.
Saprotrophs
Saprotrophs are organisms that extract nutrients from dead organic material. Fungi, classified as saprotrophs, form a number of digestive enzymes. If a saprotroph is capable of secreting digestive enzymes of three main classes, namely 1) enzymes that break down carbohydrates, such as amylases (break down starch, glycogen and related polysaccharides), 2) lipases (break down lipids) and 3) proteinases (break down proteins), then it can use a variety of substrates. Kinds Penicillium form green and blue molds on substrates such as soil, raw leather, bread and rotting fruit.
The hyphae of saprotrophic fungi usually exhibit positive chemotropism. In other words, they grow towards certain substrates, reacting to substances diffusing from these substrates.
Saprotrophic fungi usually produce large numbers of light, resistant spores. This allows them to easily spread to other power sources. Examples of such mushrooms include Mucor, Rhizopus And Penicillium.
Saprotrophic fungi and bacteria together form a group of decomposers that play an important role in the cycle of nutrients in nature. A particularly important role is played by those few fungi that secrete cellulase and lignase, which break down cellulose and lignin, respectively. Because cellulose and lignin (complex compounds found primarily in wood) are important structural elements of plant cell walls, decay of wood and other plant debris occurs in part as a result of the activity of decomposers that secrete cellulase and lignase.
Some saprotrophic fungi are of economic importance. This is, in particular, Saccharomyces(yeast) used in brewing and baking, and Penicillium(section 12.11.1), used in medicine.
Mutualism (symbiosis)
Fungi are involved in the creation of two very important types of symbiotic unions - lichens and mycorrhizae. Lichens are a symbiotic association of a fungus and algae - green or blue-green (cyanobacteria). Lichens usually live on exposed rocks or tree trunks; in damp forests they also hang from trees. It is believed that the algae supplies the fungus with organic products of photosynthesis, and the fungus, being protected from strong sunlight, is able to absorb water and mineral salts. The fungus can also store water, which allows lichens to grow in conditions where no other plants can exist.
Mycorrhiza is an association of a fungus and plant roots. The fungus absorbs mineral salts and water, supplying them to the tree, and in return receives organic products of photosynthesis. Mycorrhiza is discussed in more detail in section. 7.10.2.
Penicillium is a plant that is widespread in nature. It belongs to the class of imperfect. At the moment there are more than 250 varieties of it. Golden pinicillus, otherwise known as racemose green mold, is of particular importance. This variety is used for the manufacture of medicine. “Penicillin” based on this fungus allows you to overcome many bacteria.
Habitat
Penicillus is a multicellular fungus for which soil is its natural habitat. Very often this plant can be seen in the form of a blue or green coating of mold. It grows on all kinds of substrates. However, it is most often found on the surface of plant mixtures.
Mushroom structure
As for the structure, the penicillium fungus is very similar to aspergillus, which also belongs to the family of moldy fungi. The vegetative mycelium of this plant is transparent and branching. It usually consists of a large number of cells. It differs from penicillium by mycelium. He has it multicellular. As for the mucor mycelium, it is unicellular.
Penicillium vultures are either located on the surface of the substrate or penetrate into it. Elevating and erect conidiophores extend from this part of the fungus. Such formations, as a rule, branch in the upper part and form brushes that bear colored single-cell pores. These are conidia. Plant brushes, in turn, can be of several types:
- asymmetrical;
- three-tier;
- two-tier;
- single-tier.
A certain type of penicillium forms bundles of conidia, which are called coremia. The fungus reproduces by spreading spores.
Is it harmful to humans?
Many people believe that penicillium fungi are bacteria. However, this is not the case. Some varieties of this plant have pathogenic properties against animals and humans. The greatest harm is caused in cases where mold affects agricultural and food products, intensively multiplying inside them. If stored improperly, penicillium infects feed. If it is fed to animals, their death is possible. After all, a large amount of toxic substances accumulate inside such food, which negatively affect health.
Application in the pharmaceutical industry
Can penicillium mushroom be beneficial? The bacteria that cause certain viral diseases are not resistant to the antibiotic, which is made from mold. Some varieties of these plants are widely used in the food and pharmaceutical industries due to their ability to produce enzymes. The drug Penicillin, which fights many types of bacteria, is obtained from Penicillium notatum and Penicillium chrysogenum.
It is worth noting that the production of this medicine occurs in several stages. To begin with, the fungus is grown. Corn extract is used for this. This substance allows you to obtain better penicillin products. The fungus is then grown by immersing the culture in a special fermenter. Its volume is several thousand liters. There the plants actively reproduce.
After being removed from the liquid medium, the penicillium mushroom undergoes additional processing. At this stage of production, salt solutions and organic solvents are used. Such substances make it possible to obtain the final products: potassium and sodium salts of penicillin.
Molds and food industry
Due to some properties, penicillium mushroom is widely used in the food industry. Certain varieties of this plant are used in cheese making. As a rule, these are Penicillium Roquefort and Penicillium camemberti. These types of mold are used in the production of cheeses such as Stiltosh, Gornzgola, Roquefort and so on. This “marble” product has a loose structure. Cheeses of this variety are characterized by a specific aroma and appearance.
It is worth noting that the penicillium culture is used at a certain stage in the manufacture of such products. For example, to produce Roquefort cheese, the mold strain Penicillium Roquefort is used. This type of fungus can multiply even in loosely compressed curd mass. This mold tolerates low oxygen concentrations very well. In addition, the fungus is resistant to high levels of salts in an acidic environment.
Penicillium is capable of secreting lipolytic and proteolytic enzymes that affect milk fats and proteins. Under the influence of these substances, the cheese acquires friability, oiliness, as well as a specific aroma and taste.
The properties of the penicillium mushroom have not yet been fully studied. Scientists regularly conduct new research. This allows us to identify new properties of mold. Such work makes it possible to study metabolic products. In the future, this will allow the penicillium fungus to be used in practice.
Microscopic fungi (Mukor, Aspergillus, Penicillium, Candida). Morphology, methods of reproduction, cultural properties. Diseases they cause in humans and laboratory methods for their diagnosis
Medicine and veterinary medicine
Fungal cells are covered with a dense cell membrane consisting of polysaccharides similar to cellulose and nitrogenous substances similar to chitin. In most fungi, the vegetative body of the mycelium consists of a system of thin branching threads called hyphae. Sexual stages are found in many pathogenic fungi belonging to the classes...
Microscopic fungi (Mukor, Aspergillus, Penicillium, Candida). Morphology, methods of reproduction, cultural properties. Diseases they cause in humans and laboratory methods for their diagnosis.
Fungal cells are covered with a dense cell membrane consisting of polysaccharides similar to cellulose and nitrogenous substances similar to chitin. In most fungi, the vegetative body (mycelium) consists of a system of thin branching threads called hyphae. Intertwined, the mycelium forms a mycelium. Hyphae are capable of growing in length and develop on the surface or inside the nutrient substrate. Accordingly, a distinction is made between substrate (vegetative) mycelium growing into the nutrient medium and aerial mycelium. The ends of the mycelium threads can be twisted in the form of spirals, curls, etc.
Fungi reproduce using various structures. During the formation of sexual spores, meiosis takes place, and conidia are non-sexual reproductive organs. Sexual stages are found in many pathogenic fungi belonging to the classes Ascomycetes and Zygomycetes.
Almost all pathogenic fungi are aerobes: a wide influx of oxygen promotes the development of mycelium and the accumulation of waste products. To feed mushrooms, nitrogen and carbon-containing substances (as well as mineral compounds) are necessary. This explains the ability of many pathogenic fungi to easily develop in the body of humans and animals. Pathogenic fungi are able to reproduce in the pH range from 3.0 to 10.0; Sporulation of fungi is facilitated by a decrease in the humidity of the nutrient medium and a reduced content of proteins and carbohydrates in the medium.
On liquid nutrient media, many fungi grow in the form of a felt-like sediment, first at the bottom, and then in the form of a wall ring or a continuous film. According to the nature of growth on solid nutrient media, fungal colonies are divided into several types (8)
Diseases caused by pathogenic fungi can be divided into two groups: systemic, or deep, mycoses and superficial mycoses.
Aspergillosis. People with aspergillosis are not infectious to others. Infection occurs almost exclusively through inhalation and, less frequently, through nutritional means, occasionally through contact when the skin and mucous membranes are damaged and fungal spores come into contact with them.
Candidiasis (candidomycosis) is an infectious disease of the skin, mucous membranes and internal organs caused by yeast-like fungi of the genus Candida. Distributed everywhere, more often found in the tropics and subtropics.
The causative agents of phycomycosis are various species of fungi of the genera Rhizopus, Mucor, Absidia, united in the Mycoaceae family of the class Phycomycetes (Zygomycetes).
As well as other works that may interest you |
|||
460. | Tractor repair workshop in Tyumen | 668 KB | |
The need for mechanisms, equipment, materials, workers by profession and qualifications. Selection of methods and methods of work production with their justification. Calculation of the number of employees and determination of the area of administrative and utility premises. Ensuring the quality of construction and installation work, safety precautions. | |||
461. | The theory of penny, penny and credit systems | 615 KB | |
The reality and economic basis of penny turnover. Methods of sovereign regulation of penny turnover. The reality and patterns of the development of inflation. Penny flows and their balancing. Constructive theory of the value of pennies. Contributions by J. Keynes and M. Friedman in the development of the theory of pennies. | |||
462. | Celestial bodies in astrophysics | 636 KB | |
Electromagnetic radiation studied in astrophysics. Photoelectric radiation receivers. Physical properties of the terrestrial planets and giant planets. Distribution of stars in the Galaxy. History of the development of astronautics. | |||
463. | Information systems and technologies | 570 KB | |
The importance of the information system, structure, principles of creation. Classification of information systems at the level of structure. Economic information as a subject of processing in information systems. Forms of presentation of economic information, the nature and means of its transmission. Hierarchical and facet classification method. | |||
464. | Microcontroller 3x3x3 LED cube | 643.5 KB | |
A 3x3x3 LED cube is a figure made up of 27 LEDs, which is important for interior design. Various areas of the 3x3x3 LED cube. Development of software and technological products, creation of microcircuits and development of software mi. | |||
465. | Construction of modern automation systems for thermal power equipment based on freely programmable controllers (PLC) | 565 KB | |
Structure of heating boiler automation subsystems. Boiler unit as an object of regulation. Tasks of the vacuum control circuit in the boiler furnace. Development of a program for assessing energy savings when implementing VFDs. Calculation of operating costs for automation. | |||
466. | Introduction to the MS DOS and Windows XP operating systems | 315 KB | |
Basic MS DOS commands. Basic commands for working with files and directories. Introduction to the Volkov Commander program. Principles of organizing multitasking work in the system. Research on methods for launching the Explorer program. | |||
467. | Gradient method for numerical optimization of nonlinear programming problems | 1.16 MB | |
Suspension of the gradient method, if applied to the area of change of changes on a daily basis. Use of the gradient method, if there is a clear delineation of the changeable x in the area. Familiarization with the gradient method of numerical optimization, gaining skills in decoupling and analysis of nonlinear programming problems using the gradient method. | |||
468. | Engineering solutions for the construction of many old-style apartment buildings | 197.5 KB | |
Familiarization with the buildings of many old-style apartment buildings, the engineering systems of these buildings, the energy saving systems of these buildings (before reconstruction, after reconstruction). | |||