Some rod-shaped bacteria, when exposed to unfavorable conditions, form round or elliptical bodies inside their cells, called spores. Almost the entire content of protoplasm is spent on their formation. First formed prospor which then turns into a dispute. The spore formation process takes from 40-50 minutes. up to several hours, and sometimes drags on for a whole day. Spore-bearing cells lose their ability to reproduce. After maturation of the spore, the remnants of the vegetative cell die off and are destroyed. Outer sheath - exine becomes impermeable to water and substances dissolved in it. Inner shell - intina plays an important role in spore germination. A shell for a new vegetative cell is built from it. The water in the spore is in a special state, the enzymes are inactive, the shell restricts the exchange of spores with the external environment - all this allows the spores to remain viable for tens and hundreds of years. Hence, spore is a resistant form of bacteria to adverse environmental conditions ... For example, when river water is boiled, all bacterial cells die, except for spore-forming ones. Spores do not die when dried, frozen, exposed to direct sunlight and strong chemical poisons. Spores die when sterilized in autoclaves (120-140˚C). However, the same bacteria form spores of different resistance, and some of the spores can be killed by prolonged boiling. When the spore gets into favorable conditions, it begins to germinate. At the same time, it swells, becomes richer in water, increasing almost twice. The outer shell is torn and the seedling emerges through the hole formed. In some bacilli, the activation of enzymes and the formation of a vegetative cell is completed in 40-50 minutes. Sometimes, when toxic substances accumulate in the environment, spore-bearing bacilli may lose their ability to sporulate.
In the process of evolution, bacteria have adapted to survive in the most unfavorable environmental conditions and retained hereditary information through the formation of spores. Bacterial spores form inside the cell. The whole process of germination (sporulation) lasts 18 - 20 hours. During this process, a number of biochemical processes change in the bacterial cell. Bacteria can be in a spore-like state for a long time - hundreds of years. Under favorable environmental conditions, spores germinate. The germination process takes 4 - 5 hours.
Spore formation occurs when:
Rice. 1. In the photo of a spore inside a bacterial cell (photo taken under the light of an electron microscope - EM).
The spore-forming rod-shaped bacteria are called bacilli. They belong to the family Bacillaceae and are represented by the genus Clostridium Clostricdium, the genus Bacillus and the genus Desulfotomaculum. They are all gram positive anaerobic bacteria.
Genus clostridium has more than 93 species of bacteria. They all form spores. of the genus Clostridium cause pulmonary gangrene, are the culprits of complications after abortion and childbirth, severe toxic infections, including botulism. The spores of this species of bacteria exceed the diameter of the vegetative cell.
Genus bacillus has more than 217 species of bacteria. Pathogenic bacteria of the genus Bacillus cause a number of diseases in humans and animals, including foodborne diseases and anthrax. The spores of bacteria of this species do not exceed the diameter of the vegetative cell.
Rice. 2. The photo shows bacteria of the genus Clostridium. Left - Clostridium perfingens. They are causative agents of foodborne disease and gas gangrene. Right - Clostridium botulinum. The bacteria cause a severe foodborne illness called botulism.
Rice. 3. In the photo, the causative agent of anthrax. Bacillus anthracis, genus Bacillus - large, immobile, with chopped off ends (left) and a bacterium in a spore-like state (right).
Before the formation of the spore itself in the vegetative bacterial cell, the metabolic rate decreases, DNA replication stops, one of the nucleotides is localized in the sporogenic zone, and dipicolinic acid begins to be synthesized.
The formation of the sporogenic zone begins with the thickening of the cytoplasmic area in which the nucleotide is located ( prospor). Isolation of the sporogenic zone occurs with the help of the cytoplasmic membrane, which begins to grow into the cell.
A cortex is formed between the inner and outer layers of the membrane. One of its components is dipicolinic acid, which determines the thermal stability of the spore.
The outward side of the membrane is covered with a membrane (exospore). It consists of proteins, lipids and other compounds that are not found in the vegetative cell. The shell is thick and loose. It is hydrophobic.
During the period of maturation of the dispute, the formation of all its structures ends. The spore acquires thermal stability. It takes on a definite shape and occupies a special position in the cage. After the full maturation of the spore, autolysis of the cell occurs.
Rice. 4. The photo shows the formed spore, along the periphery of which there are remnants of the cytoplasm.
Rice. 5. The photo on the left shows a newly formed spore (A), along the periphery of which there are remnants of the cytoplasm. Further, the cytoplasm dies off. In the photo on the right (B) the spore, purified in laboratory conditions.
Rice. 6. In the photo above, the stage of sporulation - from the formation of the sporogenic zone to the complete formation and lysis of the remnants of the cell. In the photo below, there is a spore with ribbon-like outgrowths. O is its outer shell, K is the cortex, C is the inner part.
The cortex protects the spore from enzymes, which are produced in large quantities by the cell at the final stage of sporulation. Their purpose is to completely destroy the mother's vegetative cell. In the absence of a cortex, bacterial spores are lysed. Cortex contains diaminopimelic acid, which provides thermal stability
The inner side of the cortex is adjacent to the inner side of the cytoplasmic membrane. During the period of spore germination, the cortex is transformed into the cell wall of the vegetative cell.
The side of the cytoplasmic membrane facing outward is covered with a membrane (exospore) during sporulation. It consists of proteins, lipids and other compounds that are not found in the vegetative cell. The shell is thick and loose. It accounts for about 50% of the volume of the dispute itself. It is hydrophobic. The outer wall of the spore is resistant to enzymes. It protects the spore from premature germination.
Rice. 7. In the photo of the dispute with outgrowths. Its core is a resting vegetative cell.
In some disputes, outgrowths are formed in the process of sporulation. They are diverse and specific. This trait for each bacterium is hereditarily fixed and constant. Spore outgrowths are composed primarily of protein. The amino acids of the protein are similar to those of keratin and collagen. The function of outgrowths on disputes has not yet been finally clarified.
Rice. 8. Types of outgrowths on spores: flagella, tubes, brush-shaped rods, wide ribbons, thorns, pins, in the form of antlers.
Rice. 9. In the photo there are spores of bacteria of the genus Clostridium. Outgrowths in the form of tubes (1 and 5), outgrowths in the form of flagella (2), ribbon-like outgrowths (3), pinnate outgrowths (4), spores on the surface of which there are thorns (6).
In a cell that is in a spore-like state, it is noted:
In the process of sporulation, the spore becomes covered with membranes - the outer membrane and the cortex. They protect the dispute from adverse environmental conditions.
Cortex contains diaminopimelic acid, which is responsible for thermal stability. Outer shell protects the dispute from premature germination and negative environmental factors.
In a spore-like state, the bacterium is resistant to elevated ambient temperatures and drying out. It is able to survive in solutions with a high salt content, to withstand prolonged boiling and freezing, radiation and vacuum, ultraviolet radiation. The spore is resistant to a variety of toxic substances and disinfectants.
The stability of the spores of pathogenic bacteria in the external environment contributes to the persistence of infection and the development of severe infectious diseases.
Bacterial spores are oval and spherical in shape. They can be located at the ends of the cell (causative agents of tetanus), closer to the center (causative agents of botulism and gas gangrene), or in the central part of the cell (anthrax bacillus). Less commonly, bacterial spores are located laterally.
Rice. 10. The photo shows the terminal endospores of C. difficile and Clostridium tetani.
Rice. 11. The photo shows the centrally located spores of the bacteria Bacillus cereus.
Rice. 12. The photo shows the terminal location of the spore in the bacterium Bacillus subtilis.
On the spores of the genus Clostridium and bacillus, caps are formed in the process of sporulation. They have a conical or crescent shape and a cellular structure. The cells resemble pouches that are filled with a gaseous substance. They are shaped like sticks or ovals. The cells help the spore to remain buoyant in the water. Even with centrifugation, spores with caps cannot be precipitated. Spore caps are formed in soil bacteria of hydromorphic soils, which formed under conditions of stagnant surface water or in the presence of groundwater.
Rice. 13. In the photo, the caps on the spores are cone-shaped (left) and sickle-shaped (right).
Rice. 14. The photo shows the structure of the bacterial spore cap. Individual gas cells (vacuoles, sacs) are oval.
sporogenesis, the process of formation of spores (See Disputes). In plant organisms - prokaryotes (see Prokaryotes), whose cells do not have typical nuclei, spores can arise: from a whole cell that has accumulated nutrients and a thickened membrane (exospores of many blue-green algae); when dividing Protoplast into a large number of spores (endospores of some blue-green algae, rice. one, one); as a result of the compaction and compression of the protoplast inside the cell membrane and the formation of a new multilayer membrane on top of it (in bacteria); with the disintegration of special areas of the mycelium into segments (in actinomycetes, rice. one , 2). In plants - eukaryotes (See Eukaryotes), which have typical nuclei, have 3 main types of spores (oo-, mito- and meiospores) and occupy different places in the developmental cycles, there can be 3 variants of C, respectively: oosporogenesis, mitosporogenesis, and meiosporogenesis ... Usually S. is understood as the formation of meiospores (meiosporogenesis). Oosporogenesis is associated with the fertilization process and, consequently, with the change of nuclear phases in the developmental cycles; ends with the formation of oospores (in many green algae and oomycetes), auxospores (in diatoms), zygospores (in zygomycetes), which are mononuclear or multinucleated zygotes. Mitosporogenesis leads to the emergence of mitospores, which are formed in several or a large number as a result of mitotic divisions (see Mitosis) of haploid [for example, zoospores of a number of algae ( rice. one , 3) and fungi], less often diploid (for example, carpospores of most Florida) cells or without division - monospores of edogonium ( rice. one , 4), bangiev, non-malion; does not lead to a change in nuclear phases. It proceeds in unicellular mitosporangia (for example, in zoosporangia of ulotrix, monosporangia of edogonium, cystocarpia of Florida), and unicellular algae, as it were, become sporangia themselves ( rice. one , 5). Mitosporogenesis can be observed during the disintegration of the mycelium, which consists of cells containing dicarions, for example, in smut and rust fungi. Meiosporogenesis is associated with a change in diplophase (See Diplophase) in the development cycles of both lower and higher plants by haplophase (See Haplophase). In lower plants, meiospores arise as a result of meiosis or shortly thereafter from mitotically divided haploid cells formed during meiosis. In algae and fungi with a haploid development cycle, S. occurs during germination of a zygote (oospore), the diploid nucleus of which, dividing meiotically, forms 4 haploid nuclei; in this case, 4 meiospores arise (for example, zoospores of Chlamydomonas, rice. one , 6, aplanospores of ulotrix), or 3 out of four haploid nuclei die off and only 1 meiospore is formed (for example, in Spirogyra, rice. one , 7), or meiosis is followed by 1-3 mitotic divisions and 8-32 spores are formed (for example, in Bangiaceae). In algae with isomorphic and heteromorphic developmental cycles, meiosporogenesis occurs in unicellular meiosporangia and is characterized by the formation of either 4 meiospores (for example, tetraspores of brown algae and most Florida, rice. one , 8), or 16-128 meiospores (for example, kelp zoospores, rice. one , 9) due to 2-5 mitotic divisions following meiosis. In the sporangia of marsupial fungi (asci, or asci), the 4 haploid nuclei resulting from meiosis divide mitotically and 8 endogenous meiospores (ascospores) are formed. In the basidia (spore-bearing organs) of basidiomycetes, after meiosis, 4 haploid nuclei appear, which move into special outgrowths on the surface of the basidia; in the future, these outgrowths with haploid nuclei, i.e., basidiospores, separated from basidia ( rice. one , 10). Higher plants form only meiospores, meiosporogenesis proceeds in multicellular sporangia. Usually, as a result of mitotic divisions of diploid cells of the archeporium, the so-called. sporocytes (meiotically dividing cells), each forming 4 spores (tetrads of spores). Equospore ferns produce morphologically and physiologically identical spores ( rice. 2 , 1), from which bisexual outgrowths develop. In heterosporous fern-like and seed plants, micro- and megasporogenesis, meiosporogenesis, occur, that is, there are two types of spores. Microsporogenesis occurs in microsporangia and ends with the formation of a large number of microspores ( rice. 2 , 2), then sprouting into male outgrowths; megasporogenesis - in megasporangia, where in a smaller number - often even 4 or 1 - megaspores ( rice. 2 , 3), sprouting into female outgrowths. The developing sporocytes and spores (in most higher plants) feed on substances obtained from the cells of the tapetum (the layer lining the sporangium cavity from the inside). In many plants, the cells of this layer, spreading out, form a periplasmodium (a protoplasmic mass with degenerating nuclei), in which sporocytes and then spores appear. In some plants, part of the sporocytes is also involved in the formation of periplasmodium. In the megasporangia (ovules) of some angiosperms, as a result of meiosis, cells with 2 or 4 haploid nuclei are formed, corresponding to 2 ( rice. 2 , 4) or 4 ( rice. 2 , 5) megaspores; from these cells female gametophytes develop - the so-called. bisporous and tetrasporic embryo sacs. For S. in protozoa, see Art. Disputes.
Lit .: Meyer KI, Reproduction of plants, M., 1937; Kursanov L.I., Komarnitsky N.A., Course of lower plants, M., 1945; Mageshvari P., Angiosperm embryology, trans. from English., M., 1954; Takhtadzhyan A. L., Higher plants, t. 1, M. - L., 1956; Poddubnaya-Arnoldi B, A., General embryology of angiosperms, M., 1964: Smith G. M., Cryptogamic botany, 2nd ed., V. 1-2, N. Y. - L. 1955; Lehrbuch der Botanik für Hochschulen, 29 Aufl., Jena, 1967.
A. N. Sladkov.
In unfavorable conditions (increase or decrease in temperature, drying, etc.), most bacteria, which can only be in a vegetative ("vegetative" - life) state, die, but some of them turn into spores - resting cells ... In the spore state, bacteria are viable, but not vital (the state of "suspended animation" - suppression of life), they do not need food, they are not able to reproduce. The ability to form spores is possessed by almost exclusively rod-shaped bacteria ... Only one spore is formed in each bacterial cell. Spores are unusually resistant to temperature, for example, spores of the causative agent - severe food poisoning - botulism - can withstand heating to 100 ° C for 5-6 hours. Spores endure drying, exposure to UV substances, etc. This exceptional resistance of bacterial spores to high temperatures is often the reason for the deterioration of cooked foods (canned food, fried and boiled products). The thermal stability of the spores can be explained by the relatively low content of free water in their cytoplasm. The dense multilayer shell protects spores well from the penetration of harmful substances. Bacterial spores can survive for tens or even hundreds of years. Once in favorable conditions, the spore absorbs water and swells, its thermal stability decreases, the activity of enzymes increases, under the influence of which the membranes dissolve, and the spore grows into a vegetative cell.
Food spoilage is caused only by the vegetative cells of bacteria. Therefore, it is necessary to know the conditions conducive to the formation of spores and their germination into vegetative cells in order to choose the right way of processing food in order to prevent spoilage under the influence of bacteria.
3. Morphological signs of molds
Ø Mushrooms make up a large group of organisms that are allocated to a separate kingdom of Mikota. The fungi kingdom includes microscopic filamentous fungi (previously called molds).
Ø They are classified as plant heterotrophic organisms - eukaryotes, devoid of chlorophyll... The type of mushroom has over 100,000 species. Representatives of microscopic filamentous fungi are fungi of the genera Aspergillus, Penicillium, (they affect grain and flour, pressed yeast, fats, bread, flour confectionery. varieties of wheat and rye. The use of flour causes acute food poisoning. They are found in dough and dough.
Ø Microscopic fungi usually develop on the surface of the substrate in the form of fluffy, cobweb-like and cotton-like formations, and some - in the form of thin deposits and films. Some mushrooms are active causative agents of spoilage of food products, goods and materials of organic origin (paper, wood, fabrics, leather goods), others are used in industry for the production of cheeses, for the production of organic acids, enzyme preparations, antibiotics, etc. Some cause diseases in plants, humans and animals.
The structure of mushrooms
Ø In terms of cell structure, molds do not fundamentally differ from the cells of bacteria and yeast, but they have one and sometimes several differentiated nuclei. The cells have a highly elongated shape and therefore resemble threads - hyphae... Their thickness is 1-15 microns. They branch strongly, forming an intertwining mass - mycelium, or mycelium... The mycelium is the body of molds. Most of the hyphae develop above the surface of the substrate (aerial mycelium), on which the reproductive organs are located, and some - in the thickness of the substrate (substrate mycelium). The hyphae in most filamentous fungi are multicellular, in their cells there are transverse septa - septa... Filamentous fungi do not have flagella and are immobile organisms.
Ø Typical is the ability of molds to develop at low substrate moisture - about 15%, and therefore they can affect dried fruits, crackers, and from non-food products - paper, leather, yarn and fabrics, the strength of which is significantly reduced. Mold fungi can also develop at subzero temperatures (up to -8 o C), therefore, during long-term storage of meat and fish, the temperature should not exceed -20 o C. They also actively affect products that have an acidic environment (fruits, pickled vegetables, cheeses, etc. .)
4. Mold propagation methods
Fungi reproduce asexually and sexually.
Ø Vegetative(asexual) breeding occurs: parts of the mycelium (any piece or piece of mycelium, falling on the nutrient substrate, can grow and give rise to a new mycelium) or separate cells oidia, formed as a result of hyphae dismemberment into separate cells, each of which can develop into a new mycelium.
Ø Reproduction is most typical for fungi by means of spores.... Spores are formed asexually and sexually.
Ø With asexual reproduction, spores are more often formed on special hyphae. In some fungi, such spores are formed at the top of the hyphae, outside of them (exospores). Such disputes are usually called conidia, and hyphae carrying conidia - conidiophores... Conidia are located on conidiophores singly, in groups, in chains, etc.
Ø In other fungi, spores form inside special cells that develop at the ends of the hyphae. These cells, usually round in shape and rather large in size (up to several microns), are called sporangia... Spores (endospores) that form in sporangia in large numbers are called sporangiospores, and hyphae carrying sporangia - sporangiophores... Ripe conidia crumble, and sporangia burst, and spores spill out of them, which germinate under favorable conditions.
Ø At sexual reproduction first, the fusion of two multinucleated mycelium hyphae occurs, which are usually short formations with a slight thickening at the ends. Then there is a pairwise fusion of nuclei. Sexual reproduction ends with the formation of special fruiting bodies.
Ø Sexual spores are located on plates or receptacles - bags.
Ø Mushrooms that can reproduce sexually are called perfect. Some fungi do not reproduce sexually at all. They are classified as imperfect.
Ø Many fungi, when unfavorable conditions occur, are capable of forming dormant stages in the form of so-called sclerotia and chlamydospores.
Ø Sclerotia are hard, usually dark formations of tightly intertwined hyphae; they come in various shapes.
Ø Chlamydospores(from the Greek "chlamydo" - a cloak, a protective blanket) are separate sections of hyphae, compacted due to dehydration, covered with a thick shell.
They are resistant to adverse environmental conditions, contain little water, and are rich in reserve nutrients. Once in favorable conditions for development, they germinate and form new mycelium or sporulation organs.
5. Yeast structure, shape, size
Yeast belongs to eukaryotic microorganisms. They constitute a group of unicellular immobile microorganisms that do not have a true mycelium. They are widespread in nature and are very often found in the soil, on fruits, especially overripe, and plant leaves. Many yeast are used in a number of industries - bakery, winemaking, alcohol production, brewing, fermentation, etc. Yeast can be considered as domesticated microorganisms. On the other hand, the development of yeast in food can cause spoilage (bloating, changes in odor and taste). The technical value of yeast is based on its ability convert sugar to ethyl alcohol and carbon dioxide ... In this regard, they have long received a common name sugar mushrooms, or saccharomycetes... Yeast is distinguished by a high content of proteins and vitamins (B 1, B 2, B 6, niacin) and therefore some of them are used as food and feed product. The addition of 1 ton of yeast to animal feed increases the weight gain by 1-1.6 tons, and allows to reduce the cost of feeding. Baker's yeast is produced in large quantities. They are grown on the waste of alcohol production, various hydrolysates and even on individual fractions of oil, in particular paraffins.
By form yeast can be oval, ovoid, round, lemon-shaped, less often - cylindrical, triangular, sickle-shaped, arrow-shaped, flask-shaped, etc.
Dimensions (edit) yeast varies in different species from 1.5 - 2 to 10 µm in diameter and up to 2 - 20 µm (sometimes up to 50 µm) in length.
Structure their cells are similar to the structure of fungal cells. Each cell has a nucleus clearly demarcated from the cytoplasm. The cellular structures of yeast perform the same functions as those of fungi.
By their nature, two groups of yeast should be distinguished:
Ø Cultural - yeast cultivated by humans for industrial and economic purposes, with a high fermentation capacity, giving food products a special taste and aroma. The individual varieties of such yeast are called races; (saccharomycetes)
Ø Wild - yeast found in the environment, causing spoilage of food products due to deep oxidation of sugars (to CO2 and water) and imparting unusual taste and smell to products. Some are capable of causing serious human diseases, affecting the mucous membranes, the central nervous system. In the bakery industry and the production of some flour confectionery products are microorganisms from the genus (Candida, Torulopsis). Reduces the activity of compressed yeast, impairs its lifting force. Sources of contamination of semi-finished products with wild yeast are compressed yeast containing from 15 to 45% foreign yeast, as well as flour and whey.
Some rod-shaped bacteria (genus Bacillus and genus Clostridium) can form spores. Usually, sporulation is induced by unfavorable environmental conditions: a change in temperature, a lack of nutrients, the accumulation of toxic metabolic products, a change in pH, a decrease in moisture content, etc. Thus, sporulation is not an obligatory stage in the development of spore-forming bacteria.
Only one spore is always formed in the cell.
The main stages of sporulation are:
1. Preparatory stage. The process is preceded by a restructuring of the genetic apparatus of the cell: nuclear DNA is pulled out in the form of a thread and concentrated at one of the poles of the cell or in the center, depending on the type of bacteria. This part of the cell is called sporogenic zone.
2. Formation of a prospor. In the sporogenic zone, dehydration and compaction of the cytoplasm occurs and this zone is dehydrated with the help of a septum formed from the cytoplasmic membrane.
Prospora - a structure located inside the cell and separated from it by two membranes.
3. Formation of spore shells. A cortical layer (cortex) is formed between the membranes, which is similar in composition to the cell wall of a vegetative cell. In addition to peptidoglycan - murein, the cortex contains calcium salt dipicolinic acid, which is synthesized by the cell in the process of sporulation. Then, on top of the membrane, a spore shell is synthesized, consisting of several layers. The number and structure of the layers are different for different types of bacteria. The shell is impermeable to water and solutes and provides greater spore resistance to external influences
4. Exit the spore from the cell. After the maturation of the spore, the shell is destroyed and the spore comes out.
The sporulation process takes several hours.
In this way, dispute - it is a dehydrated cell covered with a multilayer membrane, which contains the calcium salt of dipicolinic acid. The main feature of bacterial spores is their high thermal stability.
Once in favorable conditions, the dispute grows. The process of converting a spore into a growing (vegetative) cell begins with water absorption and swelling. In this case, profound physiological changes occur: respiration intensifies and enzymes are activated. During the same period, the spore loses its thermal stability. Then its outer shell is torn and a vegetative cell is formed from the formed structure.
Movement of bacteria
Among bacteria there are mobile and immobile forms. Most motile bacteria actively move only in a liquid medium.
The movement of bacteria is carried out:
· With the help of flagella;
Flagella have rod-shaped bacteria and some convoluted forms. The presence of flagella, their location are constant signs for a given species and have diagnostic value. Some types of bacteria have one flagellum. (monotrichs), in others, flagella are arranged in bundles at one or both ends of the cell (politrichs), u others cover the entire surface of the cell (peritrichs).
The length of the flagella can be many times the length of the bacterial cell, reaching 10-30 microns or more. The transverse size of the flagella is 0.01-0.03 microns.
The speed of movement of bacteria is high. In one second, a cell can travel a distance 20-50 times the length of its body. Movement occurs when the flagella rotate around its axis or due to the contraction of the flagella.
Rice. 3.1 Location of flagella:
1- monotrichial arrangement;
2- polytrichial arrangement;
3- peritrichous location
By sliding;
Typical for bacteria with a slimy sheath. Due to the mucus, the cell slides over the surface and moves.
By crawling;
The movement is carried out by contraction of the entire cell. This type of movement is carried out by spirochetes.
Jet propulsion;
Some bacteria throw out portions of mucus for movement and repel themselves at the same time.
Reproduction of bacteria
For prokaryotes, cell division into 2 parts is characteristic (binary division).
During division, circular DNA is attached to the cytoplasmic membrane, unlaced. In this case, 2 chains of nucleotides are formed, which are complementary completed, as a result of which two circular double-stranded DNA molecules are formed.
In the overwhelming number of gram-positive bacteria, division occurs exactly in half with the help of a transverse septum (set), which is formed due to the protrusion of the cytoplasmic membrane inside the cell.
In gram-negative bacteria, division occurs through the formation of a constriction (the cytoplasmic membrane and the cell wall bend to merge with the opposite cell surface).
A small proportion of bacteria multiply by budding (stem bacteria).
Classification of prokaryotes
Currently, there are several classifications of bacteria. Most famous and widely used classification of bacteria Bergi. The compilers of the Bergi Brief Guide to Bacteria, the ninth edition of which was released in 1980, aimed to create a guide that would allow bacteria to be quickly identified by a set of specific traits.
According to this classification, the kingdom of prokaryotes, depending on the attitude to light, is divided into 2 sections: department of cyanobacteria(photosynthetic) and department of animal bacteria(non-photosynthetic) . In turn, the department of scotobacteria is divided into 19 groups, each of which is divided into orders, families, genera and species depending on the shape, structure of the cell wall, characteristics of reproduction, mobility, ability to form spores, attitude to oxygen, etc.
For instance, group 8 has the name "Gram-negative facultative anaerobic rods". Some bacteria of this group (family Enterobacteriacea) are common intestinal inhabitants (genus Escherichia), others are causative agents of foodborne infections (genus Shigella, genus Salmonella).
In some groups, species are grouped into genera, which are described in a random sequence, in others, the genera are grouped into families and orders,
In recent years, it has also received recognition Murray bacteria classification, proposed in 1978. This classification is based on the structure of the cell wall. Gram + bacteria are assigned to the Firmacutes division. Another division - Gracilicutes - unites all bacteria that have a cell wall characteristic of Gram bacteria. The third section unites special forms of bacteria, devoid of a real cell wall - the Mycoplasma section.
The Gram + bacteria division includes four groups; the division into groups is based on the shape of the cells and the ability to form spores. These are cocci, spore-forming and non-spore-forming rods, actinomycetes and related microorganisms. The genus Lactobacillus belongs to the non-spore-forming Gram + rods. These are lactic acid bacteria that are used in the production of fermented milk products, in cheese making, in pickling vegetables, in baking.
All representatives of Gram bacteria do not form spores and differ sharply in their ability to develop in the light and without it. In food production, there are Gram bacteria that are indifferent to light. They differ in the shape of their cells and the way they move. In terms of the number of representatives and significance in nature and in human life, the most interesting of them are pseudomonads, enterobacteria, and acetic acid bacteria.
Self-test questions
1. What are the main cell forms in bacteria?
2. What is the difference between streptococci and staphylococci?
3. What is the relative position of the cocci have sarcins?
4. How do rod-shaped bacteria differentiate?
5. How is movement carried out in bacteria?
6. What are monotrichs and politrichs?
7. How are flagella located in mobile forms of bacteria?
8. List the convoluted forms of bacteria known to you.
9. What is the process of sporulation in bacteria?
10. What is the function of sporulation in bacteria?
11. What signs are used to determine the type of bacteria?
12. How does bacteria multiply?
13. What is the role of the nucleoid in the reproduction of bacteria?
14. What classifications of bacteria do you know?
15. Describe the following groups of bacteria: streptococci, diplobacteria, torroids, spirochetes, vibrios, prostheses, actinomycetes.
16. What signs are used as the basis for the classification of bacteria according to Bergi?
17. What is the difference between cyanobacteria and scotobacteria?
18. What signs are used as the basis for the classification of bacteria according to Murray?
19. What are actinomycetes?
20. What are "bacilli" and "clostridia" and what are their differences?
21. What are disputes?
22. Are all bacteria capable of sporulation?
23. List the main stages of sporulation in bacteria.
24. What new forms of bacteria do you know?
25. What mutual arrangements of rod-shaped bacteria do you know?
Literature
1. Schlegel G. General microbiology. -M .: Mir, 1987.- 500 p.
2. Mudretsova-Wyss K.A. Microbiology. -M .: Economics, 1985.- 400.
3. Churbanova I.N. Microbiology. - M .: Higher school, 1987. - 240 p.
4. Chebotarev L.N., Bogdanova L.V., Luzina N.I. Technical microbiology. Tutorial. - Kemerovo, publishing house KuzPI, 1986.
5. Chebotarev L.N. Microbiology in illustrations and diagrams. Tutorial. - Kemerovo, publishing house KuzPI, 1988. - 92 p.
6. Verbina NM, Kaptereva Yu.V. Microbiology of food production, Moscow: Agropromizdat, 1988, 256 p.
7. Asonov N.R. Microbiology. - 3rd edition, rev. and additional - M .: Kolos, 1997. - 352 p.
Topic 4 EUKARIOTS(mushrooms and yeast)
4.1 Microscopic fungi, their features
4.2 Reproduction of mushrooms
4.3 Classification of mushrooms. Characteristics of the most important representatives of various classes
4.4 Yeast Their shape, size Propagation of yeast. Yeast classification principles
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