One of the three kingdoms of eukaryotes (the supdomain, which includes organisms with a separate nucleus in the cells) is fungi. They are located on the border between plants and animals. Today, there are about 100 thousand species, most of which are microscopic fungi. This article tells about the features of their structure and reproduction, significance in nature and human economic activity.
Almost plants and not quite animals
The kingdom of Mycota includes both unicellular and multicellular organisms with a very peculiar organization. They have similarities with both animals and plants, namely:
- They have a cell wall, but not from cellulose, like plants, but from chitin, like animals.
- In the cells of the fungi there are vacuoles filled with cell juice. But not with starch (in plants), but with glycogen (in animals).
- Mushrooms are not capable of active movement. They lead an attached lifestyle.
- Mushrooms are heterotrophs; they do not have chlorophyll and are not capable of photosynthesis. Therefore, they feed on prepared organic substances of dead organisms (saprotrophs) or living organisms (parasites).
- In contrast to animals and plants, fungi cells have practically no differentiation into tissues, and tissues into organs.
Mysterious creatures of the devil
That is what mushrooms were considered in the Middle Ages. One of the French naturalists, Wenyang, wrote in 1727 that mushrooms exist in order to upset the harmony of all living things.
The question of the origin of mushrooms remains open today. Although back in the 18th century, the outstanding botanist Karl Linnaeus attributed these organisms to the hotel kingdom. Fungi, which arose at the dawn of the birth of life on the planet (about a billion years ago), are waiting for clues of their origin from biologists, biochemists, geneticists and systematists.
Mushroom taxonomy
All mushrooms are divided into 4 classes (lower mushrooms - Oomycetes and Zygomycetes, higher - Ascomycetes and Basidomycetes). The main criterion for separation is the presence or absence of flagella in gametes and the type of sexual reproduction. In addition, in lower fungi, the mycelium is similar to one multinucleated cell, and in higher ones, the mycelium has intercellular septa.
Most mushrooms are microscopic in size. Most often, their mycelium is not visible without magnification or visible in the form of thin threads. The presence of microscopic fungi is evidenced by the results of their vital activity - the destruction of plant, animal tissues or materials. A very small group of fungi can form fruiting bodies - dense clusters of mycelium.
The structure of microscopic fungi
Micromycetes do not form fruiting bodies; they can be unicellular or multicellular. Accordingly, the morphology of microscopic fungi is quite diverse.
The body of multicellular fungi is formed by sequentially placed cells that make up hyphae (filaments) with a thickness of 0.15 to 1 μm. Hyphae grow apically (apex) and can have a branched structure. The entire set of fungal hyphae is called mycelium or mycelium.
Mushroom hyphae grow very quickly. In some specimens in just a day, mycelium can grow tens of meters.
Unicellular fungi (for example, Yeast) are a single cell, they do not form mycelia. It has a core, vacuoles with organic and inorganic substances, mitochondria.
Features of nutrition and life
Microbiology of microscopic fungi has its own characteristics. Hyphal cells on top of the cytoplasmic membrane contain a membrane that consists of chitin polysaccharide. In the cytoplasm of the cell is the nucleus (one or more) and organelles.
Mushrooms absorb nutrients on the entire surface of the mycelium, which penetrates the entire substrate (substrate mycelium) or is located on its surface (surface mycelium).
Food for the fungus is organic compounds - sugar, polyhydric alcohols, fats, proteins. At the same time, a rich and diverse enzymatic apparatus allows the full use of the entire substrate for building the body of microscopic fungi.
Microbiology isolates fungi that are characterized by saprotrophic (feed on dead organics) and parasitic (feed on living organics) types of nutrition. In addition, fungi can enter into symbiotic relationships with plants. So, hyphae of fungi and algae form symbiotic organisms - lichens.
Microscopic pathogenic fungi can develop in animals and plant organisms and cause diseases called mycoses.
Propagation Features
Micromycetes are characterized by three types of reproduction: vegetative, asexual, and sexual.
Vegetative propagation of microscopic fungi is carried out by particles of mycelium. For example, a piece of hyphae gives rise to a new mycelium of the fungus.
Asexual reproduction is carried out using spores - microscopic rudiments that form in sporangia (specialized parts of the mycelium). The main function of the spores is survival in adverse conditions. And for a number of microscopic fungi that lead a parasitic lifestyle, spores serve to infect the host organism.
The forms of the sexual process in fungi are diverse and are divided into three groups:
- Gametogamy is a type of sexual reproduction with the formation of germ cells (gametes).
- Somatogamy is a fusion of vegetative cells of the mycelium or unicellular mushrooms.
- Gametangiogamy is a type of sexual reproduction when structures merge in which gametes are not yet differentiated.
When gametes merge (fertilization), a zygote with one or more nuclei forms in fungi. Most often, the zygote does not germinate immediately, but after a period of rest. So mushrooms can also survive adverse environmental conditions.
Micromycetes in nature
The importance of microscopic fungi in nature is enormous. They participate in the cycle of substances, decomposing organic remains along with bacteria.
Soil fungi participate in the formation of the fertile layer. In symbiosis with algae as a part of lichens, they are the first to populate poor soils and take an active part in the destruction of rocks.
It is worth noting the phenomenon of mycorrhiza - the cells of a microscopic fungus enter into symbiotic relationships with plants. At the same time, plants give the fungus organic nutrients, and the fungus produces vitamins and nitrogen-containing substances necessary for plant growth and development.
Microscopic fungi are present in all biocenoses and fulfill an important ecological function. They are an important detrital link in food chains and regulators of the numbers of other organisms. In many biogeocenoses, the proportion of fungal biomass from the biomass of all microorganisms is up to 90% and is comparable with the biomass of the roots of higher plants.
One cannot fail to note the role of microscopic pathogenic fungi in nature. They regulate the number of other organisms and participate in changes in biocenoses on the planet.
Micromycetes and man
In its activity, man has long been using some lower mushrooms.
In the bakery, dairy, brewing, wine and alcohol industries, microscopic mold fungi are used: white mold and aspergillus, all types of yeast.
In the pharmaceutical industry, micromycetes are widely used to produce antibiotics, vitamins, hormones, enzymes, and physiologically active substances.
Many micromycetes destroy paper and cellulose products, spoil oils and oil products, damage optics and works of art.
Mold and yeast are the main culprits of food spoilage. They are also wood destructive - damage wood.
Microscopic pathogenic fungi cause diseases of crops, domestic animals and humans. Due to the ability to toxin formation, fungi often become the cause of poisoning.
Mycotoxins
Hazardous biological substances synthesized by microscopic fungi are metabolites (waste products) with a variety of chemical structures and effects on the human body.
Today, more than 250 types of micromycetes are known. They synthesize about 100 toxins and allergens. Microscopic fungi of different species can synthesize the same toxin. And the poisons themselves most often have a cumulative (cumulative) effect on the human body, namely:
- Yaflatoxins - have a hepatotoxic, mutagenic, immunosuppressive effect on the human body.
- Trichotecenes - neurotoxins, inhibit the immune system, cause various dermatitis.
- Ochratoxins - affect primarily the tubules of the kidney nephrons.
- Patulins are neurotoxins and mutagens.
In case of poisoning with toxins, micromycetes should first rinse the stomach.
Parasitic micromycetes
This group includes a huge number of fungi that cause various pathologies in people, plants, animals, fish. Pathologies of the skin are called dermatomycoses, and organs - mycoses.
The most common human diseases caused by parasitic fungi are:
- Dermatophytosis (scab or ringworm), which is manifested by red itchy spots on the skin and the destruction of hair follicles.
- Candidiasis (thrush) is caused by representatives of the genus Candida, which are optionally pathogenic and are part of the normal microflora of the oral cavity, genital tract and large intestine.
- Onychomycosis (nail fungus) is caused by various fungi that affect the subungual space.
- Sporotrichosis - parasitic fungi destroy the subcutaneous tissue, mucous membranes, and internal organs.
- Black and white pedestal is a disease in which the hair follicles of the mustache and eyebrows are affected. The causative agent is a fungus of the genus Piedraia.
And this is not a complete list of diseases caused by micromycetes. At the same time, the pathways of ingestion of the fungus are diverse (air, water, contacts), and their resistance to various environments is quite high.
The most famous micromycetes
Microscopic fungi include Mucor, Penicillus and Yeast.
Mushrooms of the genus Mucor are 60 species of mushrooms, which we call white mold. Colonies form white and gray, which, as the spores mature, become black. Mycor has unicellular mycelium; the cell wall contains nitrogen-containing carbohydrate chitosan, which has allergenic characteristics. Among them there are parasites, but there are also those that are actively used in the manufacture of antibiotics. Mushroom Chinese Mukor - the basis of "raga" sourdough based on soy and cereals.
Penicillium (Penicillium) is a genus of microscopic fungi that are distributed everywhere - in soil, water, seas, air, rooms, on all surfaces. Forms greenish colonies. Golden penicillus or green racemose is the most common member of the genus and the source of penicillin. These fungi have branching multicellular mycelium.
Yeast is a group of diverse unicellular fungi from different classes (1,500 species from the class of ascomycetes and basidomycetes). These fungi do not form mycelia, and their cells are up to 40 microns in size. They are combined into a general group for the characteristics of metabolism - they all receive energy during fermentation (a redox process that decomposes carbohydrates, and the decay products are alcohols). Bakery, winemaking, brewing and kvassovar - not a complete list of industries where people use these mushrooms. And at the same time, this is one of the main factors of food spoilage, and some are parasites that cause diseases in humans (candidiasis, cryptococcosis, pitiriasis, folliculitis, seborrheic dermatitis).
"Hunting" inclinations
Oddly enough, but among microscopic fungi there are active "predators".
Thus, the fungus Arthrobotrys oligospora creates a network with its hyphae, the walls of which are covered with a sticky substance. The fungus victims are roundworms (nematodes) living in the soil. A worm adhering to gifs is deprived of the opportunity to free itself, and gifs quickly grow into its body. The nematode becomes food and after 24 hours only a shell remains of it.
Another mold fungus, Dactylaria Candida, forms a lasso ring from the hyphae. The nematode falls into it and the ring closes. The epilogue of the drama is the same as in the previous version.
These features of soil micromycetes have long been studied by biologists for use in the form of biological protection of crops.
Environmental bioindicators
Recent studies of biologists have proven that microscopic fungi have the ability to change their numbers and composition depending on the state of the environment.
Normally, the number of soil micromycetes is about 10 tons per hectare, and at the same time it is diverse. In the study of soils contaminated with oil and its products, ecologists found that at high doses of toxins, the amount and species composition of microscopic soil fungi changes dramatically. In this case, species diversity decreases sharply, micromycetes with rapid growth begin to prevail, which are not characteristic in such soils. In addition, many of these fungi are phytopathogenic - they produce biologically active substances that disrupt intracellular processes in plant organisms, which leads to inhibition of their vital activity and death.
Thus, indicators of the abundance and species composition of microscopic fungi can be reliable indicators of soil pollution by oil and its derivatives.
Summarize
For millennia, the removal of fat from the skin was considered the most labor-intensive process in the leather industry. The process was long and dirty - pigeon droppings and dog excrement were used. Today, proteinase, an enzyme that is obtained from Aspergillus mushrooms, has reduced this process to 24 hours, in addition, it has made the skin softer and easier to stain.
This is just one example of how useful microscopic organisms can be. Despite the development of biology, many features of the life of these organisms are still a mystery.
Systematists annually describe more than a thousand new species of microscopic fungi. The role of soil micromycetes remains the most unexplored branch of both bioecology and biogeography. And this is primarily due to the difficulties of observing such organisms in their natural habitat.
A new section in mycology - the study of mushroom toxins - today gives us the hope of victory over cancer. For example, the Chaga fungus toxin greatly increases the body's resistance to the development of cancer cells. And psilobicin gives good prerequisites in the treatment of nervous disorders. Even the studied penicillin continues to amaze microbiologists - most recently, scientists have managed to isolate substances from it that are close in chemical composition to the hormones liberins.
Mushrooms will not stand aside in the development of new biological means of protecting crops of agricultural plants, and in the development of new "green" methods of waste disposal.