Do bacteria have a nucleus? Bacteria. Bacterial cell shapes

In electron microscopy of ultrathin sections, the cytoplasmic membrane is a three-layer membrane (2 dark layers 2.5 nm thick are separated by a light intermediate layer). In structure, it is similar to the plasmalemma of animal cells and consists of a double layer of phospholipids with embedded surface and integral proteins, as if penetrating through the structure of the membrane. With excessive growth (compared to the growth of the cell wall), the cytoplasmic membrane forms invaginates - invaginations in the form of complex twisted membrane structures, called mesosomes. Less complexly twisted structures are called intracytoplasmic membranes.

Cytoplasm

The cytoplasm consists of soluble proteins, ribonucleic acids, inclusions and numerous small granules - ribosomes, responsible for the synthesis (translation) of proteins. Bacterial ribosomes have a size of about 20 nm and a sedimentation coefficient of 70S, in contrast to the 80S ribosomes characteristic of eukaryotic cells. Ribosomal RNAs (rRNAs) are conserved elements of bacteria (the “molecular clock” of evolution). 16S rRNA is part of the small ribosomal subunit, and 23S rRNA is part of the large ribosomal subunit. The study of 16S rRNA is the basis of gene systematics, allowing one to assess the degree of relatedness of organisms.
The cytoplasm contains various inclusions in the form of glycogen granules, polysaccharides, beta-hydroxybutyric acid and polyphosphates (volutin). They are reserve substances for the nutrition and energy needs of bacteria. Volutin has an affinity for basic dyes and is easily detected using special staining methods (for example, Neisser) in the form of metachromatic granules. The characteristic arrangement of volutin granules is revealed in the diphtheria bacillus in the form of intensely stained cell poles.

Nucleoid

Nucleoid is the equivalent of a nucleus in bacteria. It is located in the central zone of bacteria in the form of double-stranded DNA, closed in a ring and tightly packed like a ball. The nucleus of bacteria, unlike eukaryotes, does not have a nuclear envelope, nucleolus and basic proteins (histones). Typically, a bacterial cell contains one chromosome, represented by a DNA molecule closed in a ring.
In addition to the nucleoid, represented by one chromosome, the bacterial cell contains extrachromosomal factors of heredity - plasmids, which are covalently closed rings of DNA.

Capsule, microcapsule, mucus

The capsule is a mucous structure more than 0.2 microns thick, firmly associated with the bacterial cell wall and having clearly defined external boundaries. The capsule is visible in imprint smears from pathological material. In pure bacterial cultures, the capsule is formed less frequently. It is detected by special methods of staining a smear (for example, according to Burri-Gins), which create a negative contrast of the substances of the capsule: ink creates a dark background around the capsule. The capsule consists of polysaccharides (exopolysaccharides), sometimes of polypeptides, for example, in the anthrax bacillus it consists of polymers of D-glutamic acid. The capsule is hydrophilic and prevents phagocytosis of bacteria. The capsule is antigenic: antibodies against the capsule cause its enlargement (capsule swelling reaction).
Many bacteria form a microcapsule - a mucous formation less than 0.2 microns thick, detectable only by electron microscopy. One should distinguish from the capsule mucoid exopolysaccharides, which do not have clear boundaries. Mucus is soluble in water.
Bacterial exopolysaccharides are involved in adhesion (sticking to substrates); they are also called glycocalyx. Besides synthesis
exopolysaccharides by bacteria, there is another mechanism for their formation: through the action of extracellular enzymes of bacteria on disaccharides. As a result, dextrans and levans are formed.

Flagella

Bacterial flagella determine the motility of the bacterial cell. Flagella are thin filaments originating from the cytoplasmic membrane and are longer than the cell itself. The thickness of the flagella is 12-20 nm, length 3-15 µm. They consist of 3 parts: a spiral filament, a hook and a basal body containing a rod with special disks (1 pair of disks in gram-positive bacteria and 2 pairs of disks in gram-negative bacteria). Flagella are attached to the cytoplasmic membrane and cell wall by discs. This creates the effect of an electric motor with a motor rod that rotates the flagellum. Flagella consist of a protein - flagellin (from flagellum - flagellum); is an H antigen. Flagellin subunits are twisted in a spiral.
The number of flagella in bacteria of various species varies from one (monotrich) in Vibrio cholerae to tens and hundreds of flagella extending along the perimeter of the bacterium (peritrich) in Escherichia coli, Proteus, etc. Lophotrichs have a bundle of flagella at one end of the cell. Amphitrichy has one flagellum or a bundle of flagella at opposite ends of the cell.

Drank

Pili (fimbriae, villi) are thread-like formations, thinner and shorter (3-10 nm x 0.3-10 µm) than flagella. Pili extend from the cell surface and consist of the protein pilin, which has antigenic activity. There are pili responsible for adhesion, that is, for attaching bacteria to the affected cell, as well as pili responsible for nutrition, water-salt metabolism and sexual (F-pili), or conjugation pili. Pili are numerous - several hundred per cell. However, there are usually 1-3 sex pili per cell: they are formed by so-called “male” donor cells containing transmissible plasmids (F-, R-, Col-plasmids). A distinctive feature of the sex pili is the interaction with special “male” spherical bacteriophages, which are intensively adsorbed on the sex pili.

Controversy

Spores are a peculiar form of resting firmicute bacteria, i.e. bacteria
with a gram-positive type of cell wall structure. Spores are formed under unfavorable conditions for the existence of bacteria (drying, nutrient deficiency, etc.. One spore (endospore) is formed inside the bacterial cell. The formation of spores contributes to the preservation of the species and is not a method of reproduction, like fungi. Spore-forming bacteria of the genus Bacillus have spores, not exceeding the diameter of the cell. Bacteria in which the size of the spore exceeds the diameter of the cell are called clostridia, for example, bacteria of the genus Clostridium (lat. Clostridium - spindle). The spores are acid-fast, therefore they are stained red using the Aujeszky method or the Ziehl-Neelsen method, and the vegetative cell in blue.

The shape of the spores can be oval, spherical; location in the cell is terminal, i.e. at the end of the stick (in the causative agent of tetanus), subterminal - closer to the end of the stick (in the causative agents of botulinum, gas gangrene) and central (in the anthrax bacillus). The spore persists for a long time due to the presence of a multilayer shell, calcium dipicolinate, low water content and sluggish metabolic processes. Under favorable conditions, spores germinate, going through three successive stages: activation, initiation, germination.

The bacterial organism is represented by one single cell. The forms of bacteria are varied. The structure of bacteria differs from the structure of animal and plant cells.

The cell lacks a nucleus, mitochondria and plastids. The carrier of hereditary information DNA is located in the center of the cell in a folded form. Microorganisms that do not have a true nucleus are classified as prokaryotes. All bacteria are prokaryotes.

It is estimated that there are over a million species of these amazing organisms on earth. To date, about 10 thousand species have been described.

A bacterial cell has a wall, a cytoplasmic membrane, cytoplasm with inclusions and a nucleotide. Of the additional structures, some cells have flagella, pili (a mechanism for adhesion and retention on the surface) and a capsule. Under unfavorable conditions, some bacterial cells are capable of forming spores. The average size of bacteria is 0.5-5 microns.

External structure of bacteria

Rice. 1. The structure of a bacterial cell.

Cell wall

The cell wall of a bacterial cell is its protection and support. It gives the microorganism its own specific shape.
The cell wall is permeable. Nutrients pass inward and metabolic products pass through it.
Some types of bacteria produce special mucus that resembles a capsule that protects them from drying out.
Some cells have flagella (one or more) or villi that help them move.
Bacterial cells that appear pink when Gram stained ( gram-negative), the cell wall is thinner and multilayered. Enzymes that help break down nutrients are released.
Bacteria that appear violet on Gram staining ( gram-positive), the cell wall is thick. Nutrients that enter the cell are broken down in the periplasmic space (the space between the cell wall and the cytoplasmic membrane) by hydrolytic enzymes.
There are numerous receptors on the surface of the cell wall. Cell killers - phages, colicins and chemical compounds - are attached to them.
Wall lipoproteins in some types of bacteria are antigens called toxins.
With long-term treatment with antibiotics and for a number of other reasons, some cells lose their membranes, but retain the ability to reproduce. They acquire a rounded shape - L-shape and can persist in the human body for a long time (cocci or tuberculosis bacilli). Unstable L-forms have the ability to return to their original form (reversion).

Rice. 2. The photo shows the structure of the bacterial wall of gram-negative bacteria (left) and gram-positive bacteria (right).

Capsule

Under unfavorable environmental conditions, bacteria form a capsule. The microcapsule adheres tightly to the wall. It can only be seen in an electron microscope. The macrocapsule is often formed by pathogenic microbes (pneumococci). In Klebsiella pneumoniae, the macrocapsule is always found.

Rice. 3. In the photo is pneumococcus. Arrows indicate the capsule (electronogram of an ultrathin section).

Capsule-like shell

The capsule-like shell is a formation loosely associated with the cell wall. Thanks to bacterial enzymes, the capsule-like shell is covered with carbohydrates (exopolysaccharides) from the external environment, which ensures the adhesion of bacteria to different surfaces, even completely smooth ones.

For example, streptococci, when entering the human body, are able to stick to teeth and heart valves.

The functions of the capsule are varied:

protection from aggressive environmental conditions,
ensuring adhesion (sticking) to human cells,
Possessing antigenic properties, the capsule has a toxic effect when introduced into a living organism.

Rice. 4. Streptococci are capable of sticking to tooth enamel and, together with other microbes, cause caries.

Rice. 5. The photo shows damage to the mitral valve due to rheumatism. The cause is streptococci.

Flagella

Some bacterial cells have flagella (one or more) or villi that help them move. The flagella contain the contractile protein flagellin.
The number of flagella can be different - one, a bundle of flagella, flagella at different ends of the cell or over the entire surface.
Movement (random or rotational) is carried out as a result of the rotational movement of the flagella.
The antigenic properties of flagella have a toxic effect in disease.
Bacteria that do not have flagella, when covered with mucus, are able to glide. Aquatic bacteria contain 40-60 vacuoles filled with nitrogen.

They provide diving and ascent. In the soil, the bacterial cell moves through soil channels.

Rice. 6. Scheme of attachment and operation of the flagellum.

Rice. 7. The photo shows different types of flagellated microbes.

Rice. 8. The photo shows different types of flagellated microbes.

Drank

Pili (villi, fimbriae) cover the surface of bacterial cells. The villus is a helically twisted thin hollow thread of protein nature.
General type drank provide adhesion (sticking) to host cells. Their number is huge and ranges from several hundred to several thousand. From the moment of attachment, any .
Sex drank facilitate the transfer of genetic material from the donor to the recipient. Their number is from 1 to 4 per cell.

Rice. 9. The photo shows E. coli. Flagella and pili are visible. The photo was taken using a tunneling microscope (STM).

Rice. 10. The photo shows numerous pili (fimbriae) of cocci.

Rice. 11. The photo shows a bacterial cell with fimbriae.

Cytoplasmic membrane

The cytoplasmic membrane is located under the cell wall and is a lipoprotein (up to 30% lipids and up to 70% proteins).
Different bacterial cells have different membrane lipid compositions.
Membrane proteins perform many functions. Functional proteins are enzymes due to which the synthesis of its various components, etc. occurs on the cytoplasmic membrane.
The cytoplasmic membrane consists of 3 layers. The phospholipid double layer is permeated with globulins, which ensure the transport of substances into the bacterial cell. If its function is disrupted, the cell dies.
The cytoplasmic membrane takes part in sporulation.

Rice. 12. The photo clearly shows a thin cell wall (CW), a cytoplasmic membrane (CPM) and a nucleotide in the center (the bacterium Neisseria catarrhalis).

Internal structure of bacteria

Rice. 13. The photo shows the structure of a bacterial cell. The structure of a bacterial cell differs from the structure of animal and plant cells - the cell lacks a nucleus, mitochondria and plastids.

Cytoplasm

The cytoplasm is 75% water, the remaining 25% is mineral compounds, proteins, RNA and DNA. The cytoplasm is always dense and motionless. It contains enzymes, some pigments, sugars, amino acids, a supply of nutrients, ribosomes, mesosomes, granules and all sorts of other inclusions. In the center of the cell, a substance is concentrated that carries hereditary information - the nucleoid.

Granules

The granules are made up of compounds that are a source of energy and carbon.

Mesosomes

Mesosomes are cell derivatives. They have different shapes - concentric membranes, vesicles, tubes, loops, etc. Mesosomes have a connection with the nucleoid. Participation in cell division and sporulation is their main purpose.

Nucleoid

A nucleoid is an analogue of a nucleus. It is located in the center of the cell. It contains DNA, the carrier of hereditary information in a folded form. Unwound DNA reaches a length of 1 mm. The nuclear substance of a bacterial cell does not have a membrane, a nucleolus or a set of chromosomes, and does not divide by mitosis. Before dividing, the nucleotide is doubled. During division, the number of nucleotides increases to 4.

Rice. 14. The photo shows a section of a bacterial cell. A nucleotide is visible in the central part.

Plasmids

Plasmids are autonomous molecules coiled into a ring of double-stranded DNA. Their mass is significantly less than the mass of a nucleotide. Despite the fact that hereditary information is encoded in the DNA of plasmids, they are not vital and necessary for the bacterial cell.

Rice. 15. The photo shows a bacterial plasmid. The photo was taken using an electron microscope.

Ribosomes

Ribosomes of a bacterial cell are involved in the synthesis of protein from amino acids. The ribosomes of bacterial cells are not united into the endoplasmic reticulum, like those of cells with a nucleus. It is ribosomes that often become the “target” for many antibacterial drugs.

Inclusions

Inclusions are metabolic products of nuclear and non-nuclear cells. They represent a supply of nutrients: glycogen, starch, sulfur, polyphosphate (valutin), etc. Inclusions often, when painted, take on a different appearance than the color of the dye. You can diagnose by currency.

Shapes of bacteria

The shape of a bacterial cell and its size are of great importance in their identification (recognition). The most common shapes are spherical, rod-shaped and convoluted.

Table 1. Main forms of bacteria.

Globular bacteria

The spherical bacteria are called cocci (from the Greek coccus - grain). They are arranged one by one, two by two (diplococci), in packets, in chains, and like bunches of grapes. This location depends on the method of cell division. The most harmful microbes are staphylococci and streptococci.

Rice. 16. In the photo there are micrococci. The bacteria are round, smooth, and white, yellow and red in color. In nature, micrococci are ubiquitous. They live in different cavities of the human body.

Rice. 17. The photo shows diplococcus bacteria - Streptococcus pneumoniae.

Rice. 18. The photo shows Sarcina bacteria. Coccoid bacteria cluster together in packets.

Rice. 19. The photo shows the bacteria streptococci (from the Greek “streptos” - chain).

Arranged in chains. They are causative agents of a number of diseases.

Rice. 20. In the photo, the bacteria are “golden” staphylococci. Arranged like “bunches of grapes”. The clusters are golden in color. They are causative agents of a number of diseases.

Rod-shaped bacteria

Rod-shaped bacteria that form spores are called bacilli. They have a cylindrical shape. The most prominent representative of this group is the bacillus. The bacilli include plague and hemophilus influenzae. The ends of rod-shaped bacteria may be pointed, rounded, chopped off, flared, or split. The shape of the sticks themselves can be regular or irregular. They can be arranged one at a time, two at a time, or form chains. Some bacilli are called coccobacilli because they have a round shape. But, nevertheless, their length exceeds their width.

Diplobacillus are double rods. Anthrax bacilli form long threads (chains).

The formation of spores changes the shape of the bacilli. In the center of the bacilli, spores form in butyric acid bacteria, giving them the appearance of a spindle. In tetanus bacilli - at the ends of the bacilli, giving them the appearance of drumsticks.

Rice. 21. The photo shows a rod-shaped bacterial cell. Multiple flagella are visible. The photo was taken using an electron microscope. Negative.

Rice. 24. In butyric acid bacilli, spores are formed in the center, giving them the appearance of a spindle. In tetanus sticks - at the ends, giving them the appearance of drumsticks.

Twisted bacteria

No more than one whorl has a cell bend. Several (two, three or more) are campylobacters. Spirochetes have a peculiar appearance, which is reflected in their name - “spira” - bend and “hate” - mane. Leptospira (“leptos” - narrow and “spera” - gyrus) are long filaments with closely spaced curls. Bacteria resemble a twisted spiral.

Rice. 27. In the photo, a spiral-shaped bacterial cell is the causative agent of “rat bite disease.”

Rice. 28. In the photo, Leptospira bacteria are the causative agents of many diseases.

Rice. 29. In the photo, Leptospira bacteria are the causative agents of many diseases.

Club-shaped

Corynebacteria, the causative agents of diphtheria and listeriosis, have a club-shaped form. This shape of the bacterium is given by the location of metachromatic grains at its poles.

Rice. 30. The photo shows corynebacteria.

Read more about bacteria in the articles:

Bacteria have lived on planet Earth for more than 3.5 billion years. During this time they learned a lot and adapted to a lot. The total mass of bacteria is enormous. It is about 500 billion tons. Bacteria have mastered almost all known biochemical processes. The forms of bacteria are varied. The structure of bacteria has become quite complex over millions of years, but even today they are considered the most simply structured single-celled organisms.

Bacteria are microscopic single-celled organisms. The structure of the bacterial cell has features that are the reason for the separation of bacteria into a separate kingdom of the living world.

Cell membranes

Most bacteria have three shells:

cell membrane;
cell wall;
mucous capsule.

The cell membrane is in direct contact with the contents of the cell - the cytoplasm. It is thin and soft.

The cell wall is a dense, thicker membrane. Its function is to protect and support the cell. The cell wall and membrane have pores through which the substances it needs enter the cell.

Many bacteria have a mucous capsule that performs a protective function and ensures adhesion to different surfaces.

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It is thanks to the mucous membrane that streptococci (a type of bacteria) stick to the teeth and cause caries.

Cytoplasm

Cytoplasm is the internal contents of a cell. 75% consists of water. In the cytoplasm there are inclusions - drops of fat and glycogen. They are the cell's reserve nutrients.

Rice. 1. Diagram of the structure of a bacterial cell.

Nucleoid

Nucleoid means “like a nucleus.” Bacteria do not have a real, or, as they also say, formed nucleus. This means that they do not have a nuclear envelope and nuclear space, like the cells of fungi, plants and animals. DNA is found directly in the cytoplasm.

Functions of DNA:

stores hereditary information;
implements this information by controlling the synthesis of protein molecules characteristic of a given type of bacteria.

The absence of a true nucleus is the most important feature of a bacterial cell.

Organoids

Unlike plant and animal cells, bacteria do not have organelles built from membranes.

But the bacterial cell membrane in some places penetrates the cytoplasm, forming folds called mesosomes. The mesosome is involved in cell reproduction and energy exchange and, as it were, replaces membrane organelles.

The only organelles present in bacteria are ribosomes. These are small bodies that are located in the cytoplasm and synthesize proteins.

Many bacteria have a flagellum, with which they move in a liquid environment.

Bacterial cell shapes

The shape of bacterial cells is different. Bacteria in the shape of a ball are called cocci. In the form of a comma - vibrios. Rod-shaped bacteria are bacilli. Spirilla have the appearance of a wavy line.

Rice. 2. Shapes of bacterial cells.

Bacteria can only be seen under a microscope. The average cell size is 1-10 microns. Bacteria up to 100 microns in length are found. (1 µm = 0.001 mm).

Sporulation

When unfavorable conditions occur, the bacterial cell enters a dormant state called a spore. The causes of sporulation may be:

low and high temperatures;
drought;
lack of nutrition;
life-threatening substances.

The transition occurs quickly, within 18-20 hours, and the cell can remain in a state of spores for hundreds of years. When normal conditions are restored, the bacterium germinates from the spore within 4-5 hours and returns to its normal mode of life.

Rice. 3. Scheme of spore formation.

Reproduction

Bacteria reproduce by division. The period from the birth of a cell to its division is 20-30 minutes. Therefore, bacteria are widespread on Earth.

What have we learned?

We learned that, in general terms, bacterial cells are similar to plant and animal cells, they have a membrane, cytoplasm, and DNA. The main difference between bacterial cells is the absence of a formed nucleus. Therefore, bacteria are called prenuclear organisms (prokaryotes).

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All living organisms on Earth are made up of cells. It can be either an independent unit of life or a component of organisms that are more complex in their organization. Much of what the cells of higher organisms have, the cells of bacteria (prokaryotes) do not have.

The main difference is the lack of a formalized core
The main difference between bacterial cells and eukaryotic cells (plants, animals and fungi) is that they do not have a clearly defined nucleus. All genetic information in bacteria is contained in a special protein complex called a nucleoid. Despite its primitive structure, the nucleoid is capable of accurately and clearly transmitting genetic data from one generation to another. The DNA of microorganisms is a highly polymeric compound, which consists of a certain number of nucleoids located in exact sequence among themselves. When this sequence is violated, a mutation of the species occurs, which leads either to the formation of a new form, or to the acquisition or loss of any properties.

Features in the transmission of hereditary information
In animals and plants, each species has a clearly defined nucleus and a certain number of chromosomes, which are responsible for the transmission of hereditary information. Bacteria, not having a clearly defined nucleus and having only one chromosome, are devoid of signs of such a phenomenon as dominance. The chromosome looks like a spiral coiled into a ring and is attached to the cytoplasmic membrane at one point. There are species with 2 or 4 chromosomes, but they are the same. In addition to chromosomes, the genotype of microorganisms also includes the following functional units:

plasmids (contain a small number of genes, their composition is variable);

IS sequences do not carry genes responsible for information; they are able to move along the chromosome and insert themselves into any part of it;

transposons (contain a structural gene that is responsible for a particular hereditary trait).

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What organelles do microorganisms lack?
Unlike animal, plant and fungal cells, bacterial cells (prokaryotes) do not have the following organelles:

lysosomes;

plastids;

mitochondria;

Golgi complex;

endoplasmic reticulum.

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Mitochondria
The presence of these organelles in plant and animal cells makes it possible to provide the necessary energy through redox processes. They are also capable of transmitting genetic information.

Golgi complex
The function of these organelles is to accumulate, change and subsequently remove substances from plant and animal cells.

Endoplasmic reticulum

It is a cellular organelle consisting of a system of tubules and vesicles. Located in the cytoplasm and bounded by a membrane. It participates in metabolic processes, ensuring the transport of substances from the outside into the cytoplasm.

In microorganisms, many of the functions of these organelles are performed by the mesosome. This structure is formed as a result of being drawn into the cell membrane. It is involved in DNA replication, in the creation of cellular partitions and in a number of other vital processes.

Differences in the life activity of prokaryotic and eukaryotic cells

The cells of microorganisms differ from the cells of animals, plants and fungi not only in their structure, they have their own characteristics in life activity.

Movement of the cytoplasm

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Photosynthesis process

Blue-green microorganisms, like plants, are capable of accumulating solar energy and producing oxygen necessary for the life of other organisms. The difference is that in bacteria the process of photosynthesis occurs on membranes, and in plants in chloroplasts.

Phagocytosis and pinocytosis

Bacteria do not have a dense cell wall, so they completely lack physiological processes such as phagocytosis and pinocytosis. Phagocytosis is the ability to capture solid particles by drawing them inward. Pinocytosis is a similar process, only liquid substances enter the cell.

Sporulation

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Reproduction
The method of bacterial reproduction is quite simple: cell division in two. An adult cell divides into two young cells, which grow, feed, and, reaching maturity, also divide. Under favorable conditions, one bacterial cell is capable of producing 72 generations per day.

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Biology lesson on the topic “Prokaryotic cell. Bacteria"

Presentation for the lesson

Attention! Slide previews are for informational purposes only and may not represent all the features of the presentation. If you are interested in this work, please download the full version.

Goals:
consolidate knowledge about prokaryotes, show the features of the structure and functioning of a prokaryotic cell, the diversity of bacteria;

reveal the role of bacteria in human life and in nature;

continue to develop the skills to compare, analyze, and draw conclusions.

Lesson type: study of material, primary consolidation of knowledge and methods of activity.

Methods: reproductive and partially search.

Equipment: tables, questionnaires, interactive equipment.

1. Organizational moment.

2. Determining the topic of the lesson.

3. Organisms: prokaryotes, eukaryotes.

4. History of discovery.

5. Features of the structure of a bacterial cell, reproduction, sporulation.

6. Application of bacteria.

7. Consolidation of knowledge, assessment.

8. Homework.

1. Organizational moment: greeting, presence of students, preparation for the lesson.

2. Determining the topic of the lesson. (Slide No. 1, 2)

The text of the slide opens one line at a time; students must determine which organisms are being discussed.

3. Work with the information sheet, analyze the contents, compare prokaryotic organisms with eukaryotic organisms.

(Information sheets are distributed in advance to each student)

Know: Bacteria are single-celled organisms, prokaryotes, mostly heterotrophs. Structure, life activity, reproduction and distribution of bacteria. Diversity of bacteria in structure, feeding method, habitat. The place of bacteria in the system of the organic world. Pathogenic bacteria and the fight against them. Use of bacteria by humans. The role of bacteria as destructive organisms in nature. (information sheets are distributed in advance to each student).

Our planet is home to a great variety of very different organisms, and all this stunning diversity can be attributed to either prokaryotes or eukaryotes, the structural features of which need to be known. The German scientist E. Haeckel was the first to draw serious attention to the significant differences between microorganisms and plants, fungi and animals. He proposed to separate them into a separate kingdom.

4. Contribution of A. Leeuwenhoek, R. Koch, L. Pasteur to the history of the discovery of bacteria. (teacher's story).

5. The teacher’s story about the features of the structure and functioning of a prokaryotic cell using the example of a bacterial cell.

(optional – E. coli).

(Working with slides No. 3-7)

Comparing the size of bacteria with the thickness of a human hair.

The structure of a bacterial cell.

6. The role of bacteria in nature.

There are many different bacteria
Harmful and useful.
How can you use them?
This is interesting.

Stories from students, teachers using additional information, presentations (slides 8-13).

The importance of bacteria for humans.

- in humans: plague, cholera, tuberculosis, dysentery, meningitis, typhus, etc.;

- in animals: bacteriosis.

Lead to food spoilage.

The role of bacteria in nature:

As a result of the activity of putrefactive bacteria, the earth is cleared of dead plants and animals.

Many bacteria take part in the geochemical processes of the formation of sulfur, phosphorus, oil, and in the nitrogen cycle.

Advances in microbiology make it possible to delegate many operations that were previously performed by technical means to the “fragile shoulders” of bacteria. A new technology for laying roads involves the use of bacterial colonies instead of asphalt pavers. A colony of bacteria slowly but surely eats the nutrient solution, producing a layer of road surface in return.

A method has been proposed to protect teeth from destruction. The teeth are coated with a layer of certain proteins, which is inoculated with special types of bacteria. The authors of the invention believe that this will protect even the roots of teeth from destruction.

Some bacteria feed on soluble calcium salts, releasing calcite, a water-insoluble mineral that is a constituent of marble. By covering the damaged surface of marble monuments with a nutrient solution and adding a culture of appropriate bacteria, it is possible to achieve uniform restoration of the surface of the monument.

“I sharpen damask knives”

Problem from the Center for Eye Microsurgery S. N. Fedorov. After cutting the retina with a scalpel, the latter is covered with a scalpel and makes a sharp radius of 30 microns out of 300... (1 micron is equal to 0.001 millimeters). How to sharpen a scalpel for your next operation? Engineers proposed a special sharpening machine, physicists - a plaza... Biologists proposed theirs - a scalpel with a microlayer of the retina is placed in a culture of bacteria that eat organic matter.

One of the most important pieces of evidence is that fingerprints are taken this way. The surface of the objects is covered with talcum powder, and then it is blown off. Where the talc remains, there is an imprint of the papillary line. If the print is clear, then identifying the villain is quite easy. What if the line - that is, a small fatty imprint of the skin - is unclear and the talc does not linger on it? How to find out the location of all, even the smallest, lines of a fingerprint? Bacteria are used to clearly capture subtle fingerprints. They are applied to the prints along with a special gel - they multiply only where the fingerprint of the papillary line lies. After 24 hours, bacterial colonies exactly follow the skin patterns. They use bacteria that live on the human body.

Recently, many reports have appeared in the press about the use of bacteria for the extraction and/or enrichment of ores. The first place (in terms of the number of publications) is occupied by iron bacteria, which use iron in their metabolism. In the USA, about 10% of the total amount of mined copper is obtained with the help of lithotrophic bacteria (feeding on inorganic matter).

7. Consolidation of knowledge, assessment. Assignments are distributed to students for individual work.

1. A cell that does not have a formed nucleus belongs to:

A. - bacteria B. - fungus

V. – plant G. – animal.

2. The carriers of hereditary information in the cell are:

A. – chromosomes B. – chloroplasts

B. – cytoplasm G. – ribosomes.

3. Organisms whose body consists of one cell that does not have a formed nucleus, feeding mainly on organic substances are:

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Structure of a bacterial cell

Cell membranes

Most bacteria have three shells:

cell membrane;

cell wall;

mucous capsule.

The cell membrane is in direct contact with the contents of the cell - the cytoplasm. It is thin and soft.

The cell wall is a dense, thicker membrane. Its function is to protect and support the cell. The cell wall and membrane have pores through which the substances it needs enter the cell.

Many bacteria have a mucous capsule that performs a protective function and ensures adhesion to different surfaces.

It is thanks to the mucous membrane that streptococci (a type of bacteria) stick to the teeth and cause caries.

Cytoplasm

Cytoplasm is the internal contents of a cell. 75% consists of water. In the cytoplasm there are inclusions - drops of fat and glycogen. They are the cell's reserve nutrients.

Rice. 1. Diagram of the structure of a bacterial cell.

Nucleoid means “like a nucleus.” Bacteria do not have a real, or, as they also say, formed nucleus. This means that they do not have a nuclear envelope and nuclear space, like the cells of fungi, plants and animals. DNA is found directly in the cytoplasm.

stores hereditary information;

implements this information by controlling the synthesis of protein molecules characteristic of a given type of bacteria.

The absence of a true nucleus is the most important feature of a bacterial cell.

Unlike plant and animal cells, bacteria do not have organelles built from membranes.

But the bacterial cell membrane in some places penetrates the cytoplasm, forming folds called mesosomes. The mesosome is involved in cell reproduction and energy exchange and, as it were, replaces membrane organelles.

The only organelles present in bacteria are ribosomes. These are small bodies that are located in the cytoplasm and synthesize proteins.

Many bacteria have a flagellum, with which they move in a liquid environment.

Bacterial cell shapes

The shape of bacterial cells is different. Bacteria in the shape of a ball are called cocci. In the form of a comma - vibrios. Rod-shaped bacteria are bacilli. Spirilla have the appearance of a wavy line.

Rice. 2. Shapes of bacterial cells.

Bacteria can only be seen under a microscope. The average cell size is 1-10 microns. Bacteria up to 100 microns in length are found. (1 µm = 0.001 mm).

Sporulation

When unfavorable conditions occur, the bacterial cell enters a dormant state called a spore. The causes of sporulation may be:

low and high temperatures;

drought;

lack of nutrition;

life-threatening substances.

The transition occurs quickly, within 18-20 hours, and the cell can remain in a state of spores for hundreds of years. When normal conditions are restored, the bacterium germinates from the spore within 4-5 hours and returns to its normal mode of life.

Rice. 3. Scheme of spore formation.

Reproduction

Bacteria reproduce by division. The period from the birth of a cell to its division is 20-30 minutes. Therefore, bacteria are widespread on Earth.

What have we learned?

We learned that, in general terms, bacterial cells are similar to plant and animal cells, they have a membrane, cytoplasm, and DNA. The main difference between bacterial cells is the absence of a formed nucleus. Therefore, bacteria are called prenuclear organisms (prokaryotes).

Autouristi.ru

Bacterial cells do not have a formed nucleus

Bacterial cells do not have a formed nucleus

Choose one, the most correct option. In what environment does the AIDS virus usually die?
1) in the lymph
2) in breast milk
3) in saliva
4) in the air

Choose one, the most correct option. Viruses have such signs of living things as
1) food
2) growth
3) metabolism
4) heredity

The AIDS virus is very unstable and is easily destroyed in air. You can become infected with it only through sexual intercourse without a condom and through a transfusion of contaminated blood.

Choose one, the most correct option. The AIDS virus infects human blood
1) red blood cells
2) platelets
3) lymphocytes
4) blood platelets

Bacterial cell structure

In the cytoplasm of bacteria, various types of inclusions have been identified, which can be solid, liquid and gaseous. They are reserve nutrients (polysaccharides, lipids, sulfur deposits, etc.) and metabolic products.

Capsule is a mucous structure, more than 0.2 microns thick, associated with the cell wall and clearly demarcated from the environment. It is detected by light microscopy in the case of staining bacteria using special methods (according to Olt, Mikhin, Burri-Gins). Many bacteria form a microcapsule - a mucous formation less than 0.2 microns, identified only by electron microscopy or by chemical and immunochemical methods. The capsule is not an essential structure of the cell; its loss does not cause the death of the bacterium. It is necessary to distinguish mucus from the capsule - mucoid exopolysaccharides. Mucous substances are deposited on the surface of the cell, often exceeding its diameter and have no clear boundaries.

The structure and composition of gram-negative microorganisms is characterized by some features. The cell wall of gram-negative bacteria is thinner than that of gram-positive bacteria and is 14-17 nm. It consists of two layers: external and internal. The inner layer is represented by peptidoglycan, which encircles the cell in the form of a thin (2 nm) continuous network. Peptidoglycan in gram-negative bacteria is 1-10%, its microfibrils are cross-linked less tightly than those of gram-positive bacteria, the pores are wider and therefore the complex of gentian violet and iodine is washed out of the wall with ethanol, the microorganisms are painted red (the color of an additional dye - fuchsin). The outer layer contains phospholipids, monopolysaccharides, lipoprotein and proteins. Lipopolysaccharide (LPS) from the cell walls of gram-negative bacteria, toxic to animals, is called endotoxin. Teichoic acids have not been found in gram-negative bacteria. The gap between the cell wall and the cytoplasmic membrane is called the periplasmic space, which contains enzymes.

Cytoplasm forms the internal environment of the cell, which unites all intracellular structures and ensures their interaction with each other.

The substance of prokaryotic capsules consists mainly of homo- or heteropolysaccharides. Some bacteria (for example, Leuconostoc) have several microbial cells enclosed in a capsule. Bacteria enclosed in one capsule form clusters called zoogels.

This Gram staining of prokaryotes is explained by the specific chemical composition and structure of their cell wall. The cell wall of gram-positive bacteria is massive, thick (20-100 nm), tightly adjacent to the cytoplasmic membrane, most of its chemical composition is represented by peptidoglycan (40-90%), which is associated with teichoic acids. The wall of gram-positive microorganisms contains small amounts of polysaccharides, lipids, and proteins. The structural microfibrils of peptidoglycan are cross-linked tightly, compactly, the pores in it are narrow and therefore the violet complex is not washed out, the bacteria are painted blue-violet.

The cytoplasm of the cell is a semi-liquid mass that occupies the main volume of the bacterium, containing up to 90% water. It consists of a homogeneous fraction called cytosol, which includes structural elements - ribosomes, intracytoplasmic membranes, various types of formation, nucleoid. In addition, the cytoplasm contains soluble RNA components, substrate substances, enzymes, and metabolic products.

Bookshelf

Glycolysis- the process of breakdown of glucose without the participation of oxygen (anaerobic). A molecule containing 6 carbon atoms is split into 2 three-carbon molecules of pyruvic acid - PVK, 2 molecules of ATP, water, 2 molecules of NAD-H.
Respiration is an aerobic process, the process of complete oxidation of glucose. There is a sequential oxidation of PVC molecules to CO2 with the formation of another ATP molecule and four electron acceptors.
Electron transport chain - hydrogen atoms are transferred to NAD+ to form NAD-H. The NAD-H molecule delivers hydrogen atoms to the respiratory chain, turning back into NAD+. The electrons of hydrogen atoms are transported along the chain, enter into redox reactions, and release energy for the synthesis of ATP. At the end of the chain a water molecule is formed.
55% of the energy is stored in the form of high-energy bonds of ATP molecules. 45% is dissipated as heat.

View- a set of individuals that have morphological and physiological similarities, freely interbreed with each other and produce fertile offspring, occupy a certain area and live in similar environmental conditions.
Type criteria: morphological, physiological, biochemical, genetic, geographical, environmental.
Population- a group of morphologically similar individuals of the same species, freely interbreeding and occupying a specific habitat in the species’ range.
Heredity- the property of preserving and transmitting signs of structure and function from parents to offspring. The characteristics recorded in the genotype are inherited.
Variability- the ability to change and acquire new characteristics within a species.
Natural selection- the main factor determining the direction of evolution. Environmental conditions play the role of a selecting factor.
As a result of driving natural selection, individuals with changes are predominantly preserved, and stabilizing selection - with stable characteristics corresponding to the environment.

Gregor Mendel- founder of genetics.
Genetics- the science of heredity and variability. Research methods used in genetics: genetic, cytogenetic, biochemical, genealogical, twin.
Genotype- the totality of all the genes of an organism.
Phenotype- the totality of all external and internal characteristics.
Different genotypes can determine the same phenotype.
Hybrid- an individual obtained from parents that differ in certain characteristics.
Different forms of the same gene that determine different manifestations of the same trait are called alleles. They are designated by letters, for example: A - gene for dark hair, and - light hair.
A trait that appears in the offspring and suppresses the manifestation of another trait is called dominant.
A trait that does not appear externally in the offspring is called recessive.
Hybrid organisms are organisms obtained by crossing genetically dissimilar parental forms.
Variability- non-hereditary (modification) and hereditary (genotypic).
The limits of modification variability of a trait are called reaction norm. The phenotype of an organism is determined by the interaction of the genotype with environmental factors.
Hereditary variability is combinative and mutational.
Mutations- sudden changes in genes or chromosomes. This changes the amount or structure of the DNA of a given organism.
There are gene (point) and chromosomal mutations. Gene mutations are associated with changes in individual genes, while chromosomal mutations are caused by changes in the number or structure of chromosomes.
Genetics is the scientific basis of selection. Selection- a science that deals with improving existing and creating new varieties of plants and animal breeds.
Basic selection methods - hybridization And selection. New methods: receiving heterosis, polyploids, experimental mutagenesis. There are spontaneous and methodical, mass and individual artificial selection, closely related and unrelated crossing, intraspecific and distant hybridization.
Biotechnology- purposeful modification and use of biological objects in the food industry, medicine, nature conservation, etc. Directions: microbiological production, cell engineering, genetic engineering.

Mitosis phases:
Prophase- spiralization of chromosomes, dissolution of the nuclear membrane, a division spindle begins to form from one centriole to another.
Metaphase- chromosomes in the equatorial plane of the cell.
Anaphase- Chromosome chromatids diverge to the poles of the cell, becoming new chromosomes.
Telophase- despiralization of chromosomes, formation of the nuclear membrane, cell septum, formation of 2 daughter cells.
During the process of mitosis, chromatids are evenly distributed between daughter cells, so that each of them receives the same set of chromosomes as in the mother cell.

Energy exchange
3 stages:
1) Preparatory (in lysosomes): molecules of substances break down with the release of energy (heat).
2) Oxygen-free (in the cytoplasm): organic substances are broken down into even simpler ones, part of the released energy goes to the synthesis of ATP.
3) Oxygen (in mitochondria): PVA molecules are oxidized to CO2 and H2O, the released energy is stored in 36 ATP molecules.
In the cells of anaerobes - microorganisms that live in an oxygen-free environment - only 2 stages of energy metabolism occur: preparatory and oxygen-free.

Plastic exchange
Plastic metabolism is characterized by reactions of the synthesis of organic substances, which involve the expenditure of energy. Both the nucleus and the cytoplasm are involved in protein biosynthesis. The nuclear chromosomes store information about the sequence of amino acids in the protein molecule. This information is encrypted using genetic code.
Genetic code is a sequence of nucleotides in a DNA molecule that determines the sequence of amino acids in a protein molecule.
The genetic code is triplet (each amino acid corresponds to a sequence of three nucleotides), non-overlapping (the same nucleotide cannot be part of two adjacent code triplets), universal (in all organisms the same amino acids are encoded by the same triplets).
Protein biosynthesis is a complex process that results in the implementation of genetic information.
Transcription- information about the structure of the protein is copied from DNA to mRNA.
Broadcast- Amino acids are joined in a specific sequence by pegtidic bonds to form a polypeptide chain.

3 main parts: plasma membrane, cytoplasm, core.
The plasma membrane separates the cell and its contents from the environment. Consists of lipids and protein molecules (external, submerged, penetrating). Ensures the flow of nutrients into the cell and the removal of metabolic products from it: diffusion, through pores, phagocytosis (proteins and polysaccharides enter), pinocytosis (liquid). Has selective permeability.
In the cells of plants, fungi, and most bacteria, there is a cell membrane above the plasma membrane that performs a protective function and plays the role of a skeleton. In plants, it consists of cellulose and is covered with polysaccharides, which ensure contact between cells of the same tissue. In mushrooms - from a chitin-like substance.
The composition of the cytoplasm includes water, amino acids, proteins, carbohydrates, ATP (adenosine triphosphoric acid), and inorganic substances. The cytoplasm contains the nucleus and organelles of the cell. The cytoplasm is permeated with protein microtubules that form the cell's cytoskeleton, thanks to which the cell maintains a constant shape.
Lysosomes- “digestive stations” of the cell, break down complex organic substances into simpler molecules.
Mitochondria- “power stations” of the cell, ATP synthesis, source of energy.
Organic substances are synthesized in plastids (plant cells). Leukoplasts- colorless plastids, accumulate starch. Chromoplasts- synthesis of carotenoids (yellow, orange, red coloring of fruits and flowers). Chloroplasts are green plastids that contain chlorophyll. Chromo- and chloroplasts are involved in photosynthesis.
Vacuoles accumulate nutrients and breakdown products in vacuolar sap. Permanent vacuoles - in a plant cell, up to 90% of the volume. Temporary vacuoles - in an animal cell, no more than 5% of the cell volume.
EPS ( endoplasmic reticulum) - synthesis of lipids and carbohydrates. ER - smooth and rough (there are ribosomes, they are involved in protein synthesis).
Cell center(2 centrioles) participates in cell division, forms a division spindle. Golgi complex- transport-storage function, formation of lysosomes, cell membrane.

Bacterial cells do not have a formed nucleus

The science of microbiology studies the structure and functioning of microorganisms.

Predatory bacteria are known to eat representatives of other types of prokaryotes.

Thus, a new spore cell appears inside the cell, surrounded by two membranes. Then, between the membranes, a cortical layer or cortex is formed, consisting of special peptidoglycan molecules.

Bacterial spores can exist in a dormant state for a long time (tens, hundreds and even thousands of years).

A number of mutants have been obtained in E. Coli, in which a cell septum is formed either in an unusual place, or, along with a septum with normal localization, an additional septum is formed close to the cell pole, and small cells (mini-cells) measuring 0.3-0. 5µm. Mini-cells, as a rule, are deprived of DNA, since during the division of the parent cell the Nucleoid does not enter them. Due to the lack of DNA, minicells are used in bacterial genetics to study the expression of gene function in extrachromosomal factors of heredity and other issues. After the cells are inoculated into a fresh nutrient medium, the bacteria do not multiply for some time - this phase is called the initial stationary or lag phase. The lag phase turns into a phase of positive acceleration. In this phase, the division of the bacterium begins. When the cell growth rate of the entire population reaches a constant value, the logarithmic phase of reproduction begins. The logarithmic phase is replaced by a phase of negative acceleration, then the stationary phase begins. The number of viable cells in this phase is constant. This is followed by a phase of population decline. They are influenced by: the type of bacterial culture, the age composition of the culture, the composition of the nutrient medium, growing temperature, aeration, etc.

Heterotrophic bacteria assimilate carbon, assimilate carbon from organic compounds of various chemical natures, easily assimilate substances containing unsaturated bonds or carbon atoms with partially oxidized valences. In this regard, the most accessible sources of carbon are sugars, polyhydric alcohols, etc. Some heterotrophs, along with the assimilation of organic carbon, can also assimilate inorganic carbon.

The cytoplasmic membrane of the bacterium adheres to the inner surface of the cell wall, separates it from the cytoplasm, and is a functionally very important component of the cell. Redox enzymes are localized in the membrane, and such important cell functions as cell division, biosynthesis of a number of components, chemo and photosynthesis, etc. are associated with the membrane system. The thickness of the membrane in most cells is 7-10 nm. Electromicroscopic method revealed that it consists of three layers: two electron-dense and intermediate electron-transparent. The membrane contains proteins, phospholipids, microproteins, a small amount of carbohydrates and some other compounds. Many cell membrane proteins are enzymes involved in respiration processes, as well as in the biosynthesis of components of the cell wall and capsule. The membrane also contains permeases that ensure the transfer of soluble substances into the cell. The membrane serves as an astronomical barrier; it has selective semi-permeability and is responsible for the entry of nutrients and metabolic waste products into the cell.
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BACTERIA

BACTERIA, simple unicellular microscopic organisms belonging to the kingdom Prokaryotae (prokaryotes). They do not have a clearly defined nucleus; most of them lack CHLOROPHYLL. Many of them are mobile and swim using whip-like flagella. They reproduce primarily by division. Under unfavorable conditions, many of them are able to be preserved inside spores, which have high resistance due to dense protective shells. They are divided into AEROBIC AND ANAEROBIC. Although pathogenic bacteria are the cause of most human diseases, many of them are harmless or even beneficial to humans, since they form an important link in the FOOD CHAIN; for example, they contribute to the processing of plant and animal tissues, the conversion of nitrogen and sulfur into AMINO ACIDS and other compounds that can be used by plants and animals. Some bacteria contain chlorophyll and participate in PHOTOSYNTHESIS. see also ARCHAEBACTERIA, EUBACTERIA, PROKARYOTES.

Bacteria exist in three main forms and types: spherical (A), called cocci, rod-shaped (bacillus, B) and spiral (spirilla, C). Cocci occur in the form of lumps (staphylococci, 1), pairs of two (diplococci, 2) or chains (streptococci, 3). Unlike cocci, which are unable to move, bacilli move freely; some of them, called peritrichia, are equipped with many flagella (4) and can swim, and monotrichium forms (5, see in the figure below) have only one flagellum. Bacilli can also form spores (6) in order to survive a period of unfavorable conditions SPIRILLA can have a corkscrew shape, such as the spirochete Leplospira (7), or can be slightly curved, with flagella, such as Spirillum (8). Images are given with a magnification of x 5000

Bacteria do not have a nucleus; instead they have a nucleoid (1), a single loop of DNA. It contains genes, chemically encoded programs that determine the structure of the bacterium. On average, bacteria have 3,000 genes (compared to 100,000 in humans). The cytoplasm (2) also contains glycogen granules (food) (3) and ribosomes (4), which give the cytoplasm a granular appearance and serve to produce protein. In many bacteria, it also contains tiny genetic elements called plasmids. Most bacteria, but not all, have rigid protective cell walls (B). They come in two main types. The first type has one thick (10-50 nm) layers. Bacteria with this cell type are called Gram-positive because they stain bright purple using Gram dye. Gram-negative bacteria have been shown to have thinner walls (1) with an additional layer of proteins and lipids on the outside (2). This type of cell does not stain purple. This difference in properties is used in medicine. The body's defense cells recognize bacteria precisely by their walls. The cell membrane (3) surrounds the cytoplasm. It is only a few molecules of proteins and lipids thick and is a barrier through which a living cell controls the entry and exit of various substances. Some bacteria move (C) using flagella (1), which are rotated by a hook (2). The energy for movement is provided by the flow of protons through the cell membrane (3), which DRIVES a disk of protein molecules (4) located in the membrane into motion. A rod (5) connects this protein “rotor” to the hook via another disc (6), which seals the cell wall.

Before the development of effective sanitation systems and the discovery of antibiotics, epidemics of serious diseases caused by bacteria swept through Europe again and again. The symptoms of many bacterial diseases are caused by the action of toxic proteins (called toxins) that are produced by bacteria. The botulinum toxin, produced by the bacterium Clostridium botulinum (which causes food poisoning), is one of the most powerful poisons known today. The tetanus toxin, produced by the related Clostridium tetani (1), infects deep and contaminated wounds. When a nerve impulse (2) causes tension in a muscle cell, the toxin blocks the relaxing part of the signal and the muscles remain tense (this is why the disease is called tetanus). In developed countries, most killer bacteria are now under control, tuberculosis is rare and diphtheria is not a serious problem. However, in developing countries, bacterial diseases are still taking their toll.

Scientific and technical encyclopedic dictionary.

See what "BACTERIA" is in other dictionaries:

Escherichia coli ... Wikipedia

BACTERIA- BACTERIA. Contents:* General morphology of bacteria.......6 70 Degeneration of bacteria............675 Biology of bacteria......676 Bacilli acidophilus .......... 677 Pigment-forming bacteria.......681 Luminous bacteria..... .......682… … Great Medical Encyclopedia

- (from the Greek bakterion rod), microorganisms with a prokaryotic type of cell structure. Traditionally, Bacteria proper refers to unicellular rods and cocci, or those united in organized groups, immobile or with flagella, contrasting... ... Biological encyclopedic dictionary

- (from the Greek bakterion rod) a group of microscopic, predominantly unicellular organisms. They belong to prenuclear forms of prokaryotes. The basis of the modern classification of bacteria, according to which all bacteria are divided into eubacteria (Gram-negative... ... Big Encyclopedic Dictionary

Group of unicellular microscope, organisms. Together with blue-green algae, B. represent the kingdom and superkingdom of prokaryotes (see), the swarm consists of types (divisions) of photobacteria (photosynthetic) and scotobacteria (chemosynthetic). Type… … Dictionary of microbiology

- (from the Greek bakteria stick). Microscopic single-celled organisms, mostly rod-shaped. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. BACTERIA Greek, from bakteria, stick. Genus of fireweeds... ... Dictionary of foreign words of the Russian language

Modern encyclopedia

bacteria- microorganisms with a prokaryotic type of cell structure, i.e. there is no nuclear envelope, no real nucleus; die from exposure to sunlight; have a sense of smell. cocci are spherical bacteria. diplococci. micrococci. streptococci. staphylococcus... ... Ideographic Dictionary of the Russian Language

Bacteria- (from the Greek bakterion rod), a group of microscopic predominantly single-celled organisms. They have a cell wall, but do not have a clearly defined nucleus. They reproduce by division. According to the shape of the cells, bacteria can be spherical (cocci),... ... Illustrated Encyclopedic Dictionary

Bacteria- (from the Greek bakterion rod), a group of microscopic unicellular organisms. Based on the type of respiration they are divided into aerobic and anaerobic, and based on the type of nutrition into autotrophic and heterotrophic. Participate in the cycle of substances in nature, performing the function... ... Ecological dictionary