“Growth beyond the limits of the individual” So, the main characters of a spectacular evolutionary performance passed before our eyes, which brought many absolutely amazing creatures onto the stage of life. With all the differences that give the undeniable originality of each vast

Growth and reproduction of microorganisms As the famous 19th century French physiologist Claude Bernard said, life is a creation. Living organisms differ from inanimate nature mainly in that they grow and reproduce. Their growth and reproduction are best observed in such

Microbes accelerate plant growth. Various plant organs produce substances that regulate and, to a certain extent, accelerate their growth. Such substances include, for example, f3-indoleacetic acid (heteroauxin). Interestingly, heteroauxin is produced and released

“Luxurious growth” Escherichia coli lived in the body of our ancestors for millions of years, even when these ancestors were not human at all. But it was not until 1885 that the species Homo sapiens and its inhabitants were officially introduced to each other. A German pediatrician named Theodor Escherich studied

1. Reproduction is growth, heredity and development Reproduction is one of the most specific and most complex properties of life. This is natural, since in evolution selection goes precisely for this ability: in the struggle for existence, those organisms that win

The division of bacterial cells is called “binary,” during which the duplicated nucleoids are associated with the plasma membrane and diverge due to the stretching of the membrane between the nucleoids, and then a constriction or septa is formed, dividing the cell in two. The nucleoid is a cyclic giant (1.6 mm) DNA molecule that forms numerous loop domains in a state of supercoiling.

The time between bacterial cell divisions averages 20-30 minutes. During this time, nucleoid DNA replication, segregation, separation of sister nucleoids and their further divergence, formation of a septum and cytotomy occur, dividing the original cell exactly in half.

It turned out that in bacterial cells, at the beginning of DNA synthesis, which begins with replication, both growing DNA molecules are associated with the plasma membrane (Fig. 330). In parallel with DNA synthesis, despiralization of loop domains occurs due to the work of a number of enzymes (topoisomerase, gyrase, ligase, etc.), which leads to the physical separation of two daughter (or sister) nucleoid chromosomes, which are still in close contact with each other. After such segregation of nucleoids, they diverge from the center of the cell, the place of their former location, by a quarter of the length of the cell in two opposite directions. As a result, two nucleoids are located in the cell. What is the mechanism of this discrepancy is as follows.

It was established that several groups of special proteins take part in the process of nucleoid divergence. One of them, Muk B, is a giant protein (mol. mass about 180 kDa, length 60 nm), consisting of a central helical section and terminal globular sections, reminiscent in structure of filamentous proteins of eukaryotes (myosin II chain, kinesin). At the N-terminus, Muk B binds to GTP and ATP, and at the C-terminus, to a DNA molecule. On this basis, the Muk B protein is considered a motor protein involved in nucleoid segregation.

In addition to the Muk B protein, bundles of fibrils containing the Caf A protein, which can bind to myosin heavy chains, like actin, participate in the divergence of nucleoids (Fig. 331).

The formation of a constriction, or septum, resembles the cytotomy of animal cells. Fibrillar thermosensitive proteins (Fts family) take part in the formation of septa. This is a group of several proteins, among which the FtsZ protein is the most studied. It is similar in most bacteria, archibacteria, and is found in mycoplasmas and chloroplasts. It is a globular protein similar in its amino acid sequence to tubulin. During cell division, all this protein is localized in the septum zone and forms a contractile ring reminiscent of actomyosin during animal cell division (Fig. 332).

In parallel with the formation of the septum, the murein layer of the bacterial cell wall grows due to the work of the polyenzymatic complex PBP-3, which synthesizes peptidoglycans.

Thus, during the division of bacterial cells, processes similar to the division of eukaryotes are observed: the divergence of chromosomes (nucleoids) due to the interaction of motor and fibrillar proteins, the formation of a constriction due to fibrillar proteins forming a contractile ring. Unlike eukaryotes, bacteria take part in these processes by completely different proteins.

Some microorganisms reproduce by sporulation (actinomycetes and fungi) and budding (yeast); some microorganisms reproduce sexually, but most of them reproduce asexually (vegetatively). Under favorable conditions, reproduction proceeds with extraordinary speed - every 20-30 minutes, the mother bacterial cell divides into two daughter cells. The daughter cell eventually becomes the mother cell and also divides. Thus, the division of bacteria proceeds in geometric progression. If such division proceeded unhindered, then after 48 hours one bacterium could give rise to hundreds of billions of cells, and after five days such a mass that would fill the basins of all seas and oceans. However, this does not happen, since microorganisms are affected by various environmental factors.

Cell division is preceded by a uniform increase in total nitrogen, RNA and protein in the cytoplasm. Then DNA replication (doubling) occurs. In a dividing cell, hydrogen bonds are broken between DNA helices and single daughter DNA helices are formed (Fig. 25).

Rice. 25. The process of binary fission of rod-shaped prokaryotes

3 - stretching the cell;

- formation of the septum;

5 - cell separation.

Immediately after DNA replication, cell elongation and the formation of a transverse septum begin due to two layers of the cytoplasmic membrane protruding towards each other. Most often, a septum is formed in the middle of the mother cell, as a result of which the daughter cells have approximately the same size. Between the layers of the septum, a cell wall is formed.

During the process of reproduction, one of the halves of the cell constantly retains flagella. At the final stage of bacterial reproduction, flagella grow in the other half.

The growth and reproduction of microorganisms depends on various environmental factors and species characteristics. Observation of the development of microorganisms cultivated in a liquid nutrient medium in closed tanks shows that for the growth of biomass, the presence of an energy source, the presence of components necessary for the synthesis of biomass, the absence of inhibitors in the medium that suppress cell growth, and maintenance in environment of the necessary physical and chemical conditions. Under these conditions, the growth of microorganisms can be divided into several successive phases or periods (Fig. 26):

1. lag phase (English lag - delay) - the period between the sowing of bacteria and the beginning of reproduction. During this period, the bacterial culture adapts to the nutrient medium. It manifests itself in the accumulation of the optimal amount of necessary enzymes, in the inactivation of some inhibitor present in the medium, in the germination of spores, etc. Under favorable conditions, bacteria increase in size and prepare to divide. The lag phase can last from 10 minutes to several hours, but on average it is 4-5 hours.

3. The phase of logarithmic or exponential growth is the period of the most intense division of bacteria. Bacteria divide every 20-40 minutes. During this phase, bacteria are especially vulnerable, which is explained by the high sensitivity of growing cells to environmental factors. The duration of exponential growth depends on the concentration of nutrients in the substrate and averages 5-6 hours.

5. The stationary growth phase is caused by the gradual depletion of the medium, the accumulation of lytic enzymes in it, and chemical inhibition of microbial cell growth by metabolic products. This phase differs from the previous one in the increased resistance of bacteria to many chemical and physical factors. By the beginning of this phase, the number of viable cells reaches a maximum level and remains at this maximum for several hours, depending on the type of microorganisms and the characteristics of their cultivation. At the end of this phase, some microorganisms experience the process of sporulation.

6. The final phase of the reproduction process - the phase of aging and death - is characterized by the death of bacteria due to depletion of the nutrient medium and the accumulation of metabolic products in it. Autolysis of microorganisms is observed as an extreme manifestation of cell instability after the cessation of growth. The duration of this phase can range from several hours to several weeks.

Date of publication: 2015-11-01; Read: 2315 | Page copyright infringement

studopedia.org - Studopedia.Org - 2014-2018 (0.002 s)…

Bacteria, like all living organisms, reproduce. This happens most often by simple transverse division in different planes. In this case, various combinations of cells are formed: paired compounds, single cells, clusters, chains, packets, etc.

Some microorganisms reproduce by sporulation (actinomycetes and fungi) and budding (yeast); some microorganisms reproduce sexually, but most of them reproduce asexually (vegetatively).

Under favorable conditions, reproduction proceeds with extraordinary speed - every 20-30 minutes, the mother bacterial cell divides into two daughter cells. The daughter cell eventually becomes the mother cell and also divides.

Thus, the division of bacteria proceeds in geometric progression. If such division proceeded unhindered, then after 48 hours one bacterium could give rise to hundreds of billions of cells, and after five days such a mass that would fill the basins of all seas and oceans. However, this does not happen, since microorganisms are affected by various environmental factors.

Cell division is preceded by a uniform increase in total nitrogen, RNA and protein in the cytoplasm.

Then DNA replication (doubling) occurs. In a dividing cell, hydrogen bonds are broken between DNA helices and single daughter DNA helices are formed (Fig. 25).

25. The process of binary fission of rod-shaped prokaryotes

1 - formation of single DNA helices;

2 - doubling (replication) of DNA;

3 - stretching the cell;

- formation of the septum;

4 - completion of the formation of the septum and the formation of a convex cell wall;

5 - cell separation.

Immediately after DNA replication, cell elongation and the formation of a transverse septum begin due to two layers of the cytoplasmic membrane protruding towards each other.

Most often, a septum is formed in the middle of the mother cell, as a result of which the daughter cells have approximately the same size. Between the layers of the septum, a cell wall is formed.

The single DNA helix in new cells serves as a template for the creation of a second helix, resulting in the formation of a DNA double helix with restored hydrogen bonds and the formation of a new nucleoid.

During the process of reproduction, one of the halves of the cell constantly retains flagella.

At the final stage of bacterial reproduction, flagella grow in the other half.

The growth and reproduction of microorganisms depends on various environmental factors and species characteristics. Observation of the development of microorganisms cultivated in a liquid nutrient medium in closed tanks shows that for the growth of biomass, the presence of an energy source, the presence of components necessary for the synthesis of biomass, the absence of inhibitors in the medium that suppress cell growth, and maintenance in environment of the necessary physical and chemical conditions.

Under these conditions, the growth of microorganisms can be divided into several successive phases or periods (Fig. 26):

Rice. 26. Typical microbial population growth curve 1 - lag phase;

2 - phase of accelerated growth; 3 — phase of logarithmic (exponential) growth;

4 - growth deceleration phase; 5 - stationary growth phase; 6 - phase of aging and death.

lag phase (eng. lag - delay) - the period between the sowing of bacteria and the beginning of reproduction. During this period, the bacterial culture adapts to the nutrient medium. It manifests itself in the accumulation of the optimal amount of necessary enzymes, in the inactivation of some inhibitor present in the medium, in the germination of spores, etc. Under favorable conditions, bacteria increase in size and prepare to divide.

The lag phase can last from 10 minutes to several hours, but on average it is 4-5 hours.

2. The phase of accelerated growth is observed after the lag phase and is characterized by an increase in the rate of division of microorganisms and accumulation of biomass.

3. The phase of logarithmic or exponential growth is the period of the most intense division of bacteria.

Bacteria divide every 20-40 minutes. During this phase, bacteria are especially vulnerable, which is explained by the high sensitivity of growing cells to environmental factors. The duration of exponential growth depends on the concentration of nutrients in the substrate and averages 5-6 hours.

4. The growth deceleration phase is a transition period from exponential growth to the stationary growth phase. During this phase, there is a depletion of the nutrients of the substrate and the accumulation of metabolic products in it, which reduces the intensity of the reproduction of microorganisms.

The stationary growth phase is caused by the gradual depletion of the medium, the accumulation of lytic enzymes in it, and chemical inhibition of microbial cell growth by metabolic products. This phase differs from the previous one in the increased resistance of bacteria to many chemical and physical factors. By the beginning of this phase, the number of viable cells reaches a maximum level and remains at this maximum for several hours, depending on the type of microorganisms and the characteristics of their cultivation.

At the end of this phase, some microorganisms experience the process of sporulation.

6. The final phase of the reproduction process - the phase of aging and death - is characterized by the death of bacteria due to depletion of the nutrient medium and the accumulation of metabolic products in it. Autolysis of microorganisms is observed as an extreme manifestation of cell instability after the cessation of growth.

The duration of this phase can range from several hours to several weeks.

Date of publication: 2015-11-01; Read: 2316 | Page copyright infringement

studopedia.org - Studopedia.Org - 2014-2018 (0.001 s)…

Reproduction of microorganisms is the binary division of unicellular microorganisms (bacteria, rickettsia, protozoa, yeast), as a result of which two new daughter full-fledged individuals are formed, endowed with the genetic information of the mother cell. Yeast-like fungi can reproduce by budding and spores; Molds and actinomycetes usually reproduce by spores.

Bacteria

They reproduce by simple transverse division.

Bacteria are haploid cells. The composition of a bacterial cell includes a capsule, a cell wall, a cytoplasmic membrane, a cytoplasm where mesosomes, ribosomes, a nucleoid, and inclusions are located. Some bacterial cells have flagella and form spores.

Unlike animal cells, such internal structures of the bacterial cell as mesosomes, ribosomes, and nucleoids do not have membranes separating them from the cytoplasm.

According to the method of nutrition, bacteria are divided into autotrophs and heterotrophs, and according to the method of respiration - into aerobes and anaerobes.

Actinomycetes

They reproduce by spores and transverse division (lacing) of hyphae.

They occupy an intermediate position between fungi and bacteria. Among the radiant fungi, there are a network of pathogenic species - causative agents of actinomycosis. Many actinomycetes are producers of antibiotics. (cm.

Antibiotics). In Bergey's Guide, actinomycetes are called streptomycetes.

Yeast

There are 2 types of yeast reproduction - vegetative (asexual) and sexual with the formation of spores. In most species of yeast, vegetative reproduction is carried out by budding, rarely by division (Schizosaccharomyces). Asporogenous. Yeast reproduces only by budding. Sexual reproduction occurs under unfavorable conditions when the yeast stops budding and turns into bags (asci) with spores - ascospores.

The sexual process consists of copulation (fusion) of 2 vegetative cells by bringing them together and forming a copulation channel, in which the fusion of parts of the plasma and the nucleus of the cells occurs, called karyogamy, with the formation of a diploid zygote, representing 2 cells connected by the copulation channel.

Reduction division, or meiosis, accompanied by a halving of the number of chromosomes, occurs immediately, without the sexual process, and the zygote turns into an ascus with 4 haploid spores, therefore the vegetative generation of such spores is haploid. Spores germinate without copulation. This is how reproduction occurs in the yeast Zygosaccharomyces. In the yeast Saccharomyces, the sexual process occurs when spores or cells germinated from them fuse to form a diploid zygote, which immediately begins to bud, forming diploid offspring.

Meiosis occurs immediately before spore formation.

Molds

Mushrooms distinguish between vegetative, sexual and asexual reproduction.

Vegetative propagation can be carried out by separating parts of the mycelium from the main mass, which can develop independently, as well as by budding the mycelium or individual cells of yeast fungi.

Sexual reproduction consists of the fusion of germ cells, resulting in the formation of a zygote.

Asexual reproduction is carried out using special formations called spores. Spores can develop inside special spore containers or at the ends of special mycelial outgrowths - conidiophores.

The main way molds reproduce is through spores. Mold grows incredibly quickly.

In ordinary bread mold, you can distinguish small black dots - sporangia, in which spores are formed. One sporangium contains up to 50,000 spores, each of which is capable of reproducing hundreds of millions of new spores in just a few days! And if the conditions are favorable, mold will quickly appear on a book, shoes or on a fallen tree in the forest.

Bacteria: The life activity of bacteria is characterized by growth- the formation of structural and functional components of the cell and the increase in the bacterial cell itself, as well as reproduction- self-reproduction, leading to an increase in the number of bacterial cells in the population.

Bacteria multiply by binary fission in half, less often by budding.

Actinomycetes, like fungi, can reproduce by spores. For one group of unicellular cyanobacteria, multiple fission (a series of rapid successive binary fissions leading to the formation of 4 to 1024 new cells) has been described. Actinomycetes, being branching bacteria, reproduce by fragmentation of filamentous cells. Gram-positive bacteria divide by ingrowth of synthesized division septa into the cell, synthesize a transverse septum from the periphery to the center with the participation of mesosomes.

and gram-negatives - by constriction (at the site of division, a gradually increasing curvature of the CPM and the cell wall inward is detected), as a result of the formation of dumbbell-shaped figures, from which two identical cells are formed. When budding, a bud forms and grows at one of the poles of the mother cell; the mother cell shows signs of aging and usually cannot produce more than 4 daughter cells.

In other bacteria, in addition to reproduction, the sexual process is observed, but in the most primitive form.

The sexual process of bacteria differs from the sexual process of eukaryotes in that bacteria do not form gametes and cell fusion does not occur. However, the most important event of the sexual process, namely the exchange of genetic material, also occurs in this case. This is called genetic recombination.

Cell division is preceded by replication of the bacterial chromosome according to a semi-conservative type (the double-stranded DNA strand opens and each strand is completed by a complementary strand), leading to doubling of the DNA molecules of the bacterial nucleus - the nucleoid. DNA replication occurs in three stages: initiation, elongation, or chain growth, and termination.

Spirochete Reproduction: Transverse fission - cell division in bacteria in which a mother cell gives rise to two daughter cells. It is carried out in three stages:

1) replication of the DNA molecule of a circular chromosome attached to the mesosome, which is also divided into two parts;

2) breeding of two daughter ring chromosomes using mesosomes;

3) separation of the cytoplasm by a transverse partition, which is formed from the periphery to the center of the cell.

Mushroom propagation:

Most fungi are capable of vegetative, asexual and sexual reproduction.

Pleomorphism is characteristic - the presence of several types of sporulation at the same time, for example, asexual and sexual.

Vegetative propagation

• Parts of mycelium.
• Specialized formations: arthrospores (oidia) with thin walls or chlamydiospores with thick walls, they are formed, with some differences, when the mycelium disintegrates into parts, and then gives rise to a new one.
• Budding of hyphae or individual cells (for example, in yeast).

Also budding are ascospores in marsupials and basidiospores in smuts. The resulting buds gradually separate, grow, and eventually begin to bud themselves.

Asexual reproduction

Asexual reproduction itself occurs through spores.

Depending on the method of formation, endogenous and exogenous spores are distinguished.

• Endogenous disputes(sporangiospores) are characteristic of lower fungi.

They are formed inside special cells called sporangia.

• Exogenous spores usually called conidia, they are found in higher and some lower fungi.

They are formed on the tops or sides of special hyphae - conidiophores, oriented vertically, which can be simple or branched.

They are covered with a dense shell, so they are quite stable, but motionless. They can be picked up by air currents or animals and transported over significant distances. During germination, a growth tube and then hyphae are produced.

Sexual reproduction

Gamete conjugation

Lower fungi are characterized by the fusion of haploid gametes through isogamy, anisogamy (heterogamy) or oogamy.

In the case of oogamy, the genitals develop - oogonia(female) and antheridia(male). During fertilization, formation occurs oospores- this is a zygote that is covered with a thick shell, spends some time in a state of rest, after which it germinates.

Speed ​​and phases of bacterial reproduction under stationary conditions.

When bacteria are grown on a liquid nutrient medium, bottom, diffuse or surface (in the form of a film) growth of the culture is observed.

The growth of a batch culture of bacteria grown in a liquid nutrient medium is divided into several phases, or periods:

1. lag phase;

2. logarithmic growth phase;

3. phase of stationary growth, or maximum concentration of bacteria;

4. bacterial death phase.

These phases can be depicted graphically in the form of segments of a bacterial reproduction curve, reflecting the dependence of the logarithm of the number of living cells on the time of their cultivation.
Lag phase is the period between the sowing of bacteria and the beginning of reproduction.

The duration of the lag phase is on average 4-5 hours. At the same time, the bacteria increase in size and prepare to divide; the amount of nucleic acids, proteins and other components increases.
The logarithmic (exponential) growth phase is a period of intensive bacterial division. Its duration is about 5-6 hours. Under optimal growth conditions, bacteria can divide every 20-40 minutes.

During this phase, bacteria are most vulnerable, which is explained by the high sensitivity of the metabolic components of an intensively growing cell to inhibitors of protein synthesis, nucleic acids, etc.
Then comes the stationary growth phase, in which the number of viable cells remains unchanged, constituting the maximum level (M-concentration). Its duration is expressed in hours and varies depending on the type of bacteria, their characteristics and cultivation.

The process of bacterial growth is completed by the death phase, characterized by the death of bacteria under conditions of depletion of the sources of the nutrient medium and the accumulation of bacterial metabolic products in it. Its duration ranges from 10 hours to several weeks. The intensity of growth and reproduction of bacteria depends on many factors, including the optimal composition of the nutrient medium, redox potential, pH, temperature, etc.

The growth rate of bacteria depends both on external conditions and on the physiological characteristics of the cell itself.

Under favorable conditions, the growth of the bacterial cell ends with reproduction. The main way most bacteria reproduce is by simply dividing the cell in half. Division is preceded by replication (doubling) of the chromosome. These two processes are closely interrelated. The frequency of replication is regulated by the rate of cell growth. Replication of the bacterial chromosome is carried out in the previously described manner (see section 3.2.5).

The study of the pattern of uniform distribution of genetic material between daughter cells formed as a result of the division of the mother cell allowed G. Jacob, S. Brenner and T. Cousin (1963) to formulate the concept of a replicon. A replicon is a unit of replication; it is a section of DNA containing regulatory elements necessary for independent replication. In bacteria, these are the chromosome and plasmids. Each replicon contains at least two loci involved in the control of replication: a structural replicator gene (initiator gene), which determines the synthesis of the initiator protein, and a special replicator site, which recognizes signals for the beginning of chromosome doubling.

After a certain period of growth, the cell reaches a certain physiological state. From the cytoplasmic membrane, the replicon receives signals about the need for chromosome replication and the cell’s readiness to divide. Under the influence of signals, the activity of the structural gene is activated and the initiator protein is synthesized.

It acts on the replicator and starts replication.
There is a coordinated interaction between the chromosome replication system and cell division: cell division is always preceded by chromosome duplication. Once replication is complete, the process of cell division begins. In gram-positive bacteria and cyanobacteria, this is accomplished by the formation of a transverse septum that divides the mother cell into two equal daughter cells.
The division occurs as follows.

At the beginning
a double-layered cytoplasmic membrane is synthesized. Then two tubercles form on the inside of the cell wall. They grow intensively and, penetrating ring-shaped inside the cell between the layers of the formed cytoplasmic membrane, form a double partition dividing the cell in half.

Division of most grammatically careful bacteria
occurs by constriction. In this case, the genomes diverge along the poles of the cell, the cytoplasmic membrane and the cell wall stretch, invaginating from the periphery to the center of the cell until they come into contact with each other. As a result, the cell is laced into two daughter cells. Cell division by the formation of a septum or constriction is called binary due to the formation of two identical daughter cells.

In addition to the described binary fission, bacteria have another known method of reproduction: budding. Bacteria of the genera Hyphomicrobium, Pedomicrobium and others, united in the group of budding bacteria, reproduce by budding.

These organisms have the appearance of elongated rods (0.5x 2 µm), sometimes pear-shaped, ending in hyphae or prostecas (outgrowths).
Reproduction in these bacteria begins with the formation of a bud at the end of the hypha or directly on the mother cell.

The bud grows into a daughter cell, forms a flagellum and separates from the mother cell. Upon reaching a mature state, the flagellum is lost and the development process is repeated.
In contrast to binary fission, during budding, the original cell remains the mother cell, and the newly formed cell remains the daughter cell.

There are morphological and physiological differences between them.
Actinomycetes reproduce by fragments of mycelium and spores. In some (the genus Micromonospora), single spores are formed on the hyphae of the vegetative mycelium, in others (the genus Streptomyces, etc.), chains of spores are formed at the ends of the hyphae of the aerial mycelium, the so-called conidiophores.

Fragments of mycelium and spores germinate under favorable conditions of humidity and temperature and give rise to new organisms.

Filamentous cyanobacteria, in addition to binary fission, reproduce by sections of trichomes and hormogonies. The latter are shortened filaments consisting of small vegetative cells of the same shape and size. When the middle cells of the trichome (threads) die, the hormogonium slips out of the sheath of the mother trichome, grows, divides, forming new trichomes.

Hormogonia, unlike the maternal trichome, do not have heterocysts and are never surrounded by a sheath.
Regardless of which way the process of bacterial reproduction occurs, the speed of this process is enormous: in 24 hours as many generations can change as a person has in five thousand years.

The rate of reproduction depends on many conditions and is different for each type of bacteria. If the necessary nutrients are present in the medium, the temperature and acidity of the medium are favorable, the division of each cell can be repeated after 20-30 minutes (E. coli). At this rate of reproduction, 472 * 1019 cells (273.72 generations) can be formed from one cell per day.

Intensive reproduction is of great biological importance for bacteria. It ensures the preservation of microorganisms on the earth's surface. When unfavorable conditions occur, they die en masse, but it is enough for a few cells to survive somewhere, and under suitable conditions they will give rise to a large progeny of cells.
The population size of microorganisms in natural habitats, for example, in soil or water, is constantly changing in accordance with changing living conditions.

But in laboratory conditions on nutrient media, changes in the population of microorganisms occur naturally.

And also in the section “REPRODUCTION OF BACTERIA”

Actinomycetes(Actinomyces) translated from Latin is a radiant mushroom, a separate group of microorganisms that has a number of morphological characteristics of a lower type of fungus and a non-spore-forming bacterium.

Morphology of actinomycetes

The structure of actinomycytes has similar features with filamentous mushrooms, mycelium vultures have an average thickness of 0.7 microns, varying between 0.5-1.2 mm, which is much less than that of mushrooms.

Straight or slightly curved threads that do not have transverse partitions are characterized by monopodial or, in some cases, whorled branching. The composition of the cell membrane has a number of features of gram-positive bacteria.

Reproduction of actinomycetes

Actinomyces reproduce using substratal mycelium germinating in the substrate and aerial mycelium growing from fruit-bearing sporangiophores.

Fruit bearers, depending on the type, have different curl shapes from twisted to straight or wavy.

Some species of actinomycetes have spore-bearing branches located in the form of whorls or bundles; they often hang monopodially on the mycelium threads.

Spore formation occurs through fragmentation or segmentation.

Fragmentation- this is the process of crushing the protoplast of a spore-bearing branch into one hundred or more small lumps containing basophilic and nuclear substances.

The lumps, turning into spores, are located in a long chain in the spore carrier.

Segmentation- this is the process of dividing the spore bearer into rod-shaped segments, with the help of transverse partitions, they are rounded and converted into spores.

The spore shells of different species have a smooth, sometimes bumpy, jagged, spiny, hairy surface. The growths on the surface of the shells are clearly visible through an electron microscope.

In most cases, actinomycetes are aerophiles and mesophiles, but thermophiles have also become widespread; many of their species are capable of producing pigments of different colors.

Actinomycetes, having a diverse set of enzymes, are able to synthesize various substances and release them in large quantities into the environment. Among these substances with high physiological activity are many vitamins, some amino acids, toxins, carotenoids, phytohormones and others.

It is also worth mentioning the ability of actinomycetes to form various types of antibiotics.

Bacteria are prokaryotes (nuclear-free), the simplest forms of organization of living organisms. You can find out what these organisms are from our article.

How bacteria reproduce: methods

There are not so many ways in which bacteria reproduce: simple division, budding, conjugation (some scientists consider this to be the sexual process in bacteria). Let's look at each of them in detail.

The most common method of reproduction in bacteria in the natural environment is equal transverse division. This means that the mother cell, after doubling the DNA strand and all organelles, divides in two, forming two daughter cells whose genetic material will be similar to the mother’s. Thus, the bacterium literally clones itself. The division process occurs through the formation of a constriction or transverse septum in the equatorial part of the cell.

Another method of reproduction that bacteria use in nature and the human body is budding, which is slightly different from division. Thus, the mother cell does not divide “in half”, but “grows” a daughter cell (bud) at one of its poles. A mother cell can most often grow up to 4 daughter cells, after which it ages and dies. Budding, like fission, produces genetic clones of the mother cell.

Sexual process in bacteria

Another way of bacterial reproduction, which involves the simplest sexual process, is conjugation. More often it is used by bacteria living in the body of humans or animals. In them, unlike eukaryotes (nuclear organisms), gametes are not formed and sex cells (gametes) do not merge.

During such reproduction, two bacterial cells come into contact, form a conjugation bridge and exchange genes, resulting in the formation of genetically new cells. This process is also called genetic recombination. Bacteria such as Escherichia coli and some other gram-negative and gram-positive bacteria reproduce sexually.

Bacterial organisms have long colonized all known habitats. They are in the air, in water, and live in other organisms. But most of them are in the upper layers of the soil. The number of these organisms depends not only on the structural features. It increases many times due to its great ability to reproduce. How bacteria reproduce will be briefly outlined in the article.

What are bacteria?

These organisms are unicellular, less often colonial organisms. They are arranged quite primitively. The surface apparatus is represented by a membrane and a mucous capsule, and the cytoplasm is devoid of mitochondria and plastids. Many cells have a flagellum with which the bacterium can move.

Genetic material

Bacteria are prokaryotes. This means that their cells lack a nucleus. But the genetic material is still present in them. Clusters of DNA molecules are located in a certain part of the cytoplasm and are called nucleoids. In other words, we can say that prokaryotes have a core without a shell. Therefore, they cannot carry out complex biochemical processes. However, this does not in any way affect their ability to reproduce.

How do bacteria reproduce?

Bacteria multiply This is the main and fastest way. From one mother cell, two daughter cells are formed in half an hour. And after the same period of time, new cells are formed again from the two daughter cells. This explains the large number of bacteria in nature.

Under unfavorable conditions, bacteria are able to form spores - cells occasionally bud - form small protrusions that grow, turn into adults and split off from the mother.

How bacteria reproduce can also be considered using the example of conjugation. This is a form of sexual process. It consists in the exchange of hereditary information between cells. Before the start, the circular DNA molecule doubles. Next, a cytoplasmic bridge is formed between the cells, along which one cell moves to another. There is an exchange of DNA sections. As a result, the body acquires new characteristics, which are most often useful for it. For example, bacteria become resistant to adverse environmental factors, viruses or antibiotics.

They live and reproduce on the roots of legumes and cereal plants. Invading the root system through affected areas or root hairs, they grow and form protrusions - nodules. A favorable environment for metabolism is created inside them. The root gives the bacteria organic substances, and the bacteria give nitrogen, which is so necessary for the growth and development of plants.

Cell division in two

How bacteria reproduce depends on their species and habitat. But all bacterial organisms are capable of dividing in two. This process occurs in several stages and is called binary fission.

Before division begins, the circular DNA molecule doubles. In other words, replication occurs. The nucleotide divides and the daughter DNAs diverge. Growing into the cytoplasm, the cell membrane is located between DNA molecules. It is she who divides the cell and its contents in half.

72 bacterial generations are born from one cell per day. If all these bacteria remained viable, their biomass would be about 5 tons. Naturally, this does not happen in nature and most bacteria die.

Vegetative propagation

The structure also determines how bacteria reproduce.

Colonial species and cyanobacteria (blue-green algae) are capable of vegetative reproduction. Plants most often reproduce in this way. It consists in separating its multicellular part from the whole organism.

Filamentous species of cyanobacteria form specialized cells called heterocysts. Vegetative propagation consists of breaking the filaments, the border of which passes at the location of the heterocysts.

Cocci may form chains, clusters, or other formations. Breaking away from each other, they also multiply.

Sporulation

Bacteria reproduce by spores that are formed when unfavorable conditions occur. Sporulation is not only a method of reproduction. A special environment is created inside the spore, the water content decreases, and vital processes are suspended. In this state, the spores are not afraid of high temperatures, ionizing radiation, or exposure to chemicals. When favorable conditions return, young bacterial organisms emerge from the spores. Thus, the formation of spores is an additional opportunity to maintain cell viability in conditions unsuitable for life. There are cases where bacterial spores remained viable for tens and even hundreds of years.

encystment

Another way of protection from unfavorable conditions and a method of reproduction is the formation of cysts. They are bubbles with thick shells. Bacteria can remain in a cyst state for a long time. However, they do not die from temperatures exceeding 200 degrees. With the onset of normal conditions, the bacterium leaves the shell and begins normal binary fission.

How bacteria reproduce is rather determined by environmental conditions. When there are not enough nutrients and moisture, there is excess oxygen, the air is too hot or cold, bacteria use the processes of encystment or sporulation. In comfortable conditions, they divide or reproduce vegetatively. It is this variety of reproduction methods that bacteria are capable of that determines their number in nature. If the process of dividing one bacterial cell did not stop for 10 days, they could cover the entire surface of the globe.