The common amoeba is a representative. Common Amoeba, structure. Amoeba habitat. Features of existence and development

The cytoplasm is completely surrounded by a membrane, which is divided into three layers: outer, middle and inner. In inner layer, which is called endoplasm, are necessary elements for an independent organism:

• ribosomes;
• elements of the Golgi apparatus;
• supporting and contractile fibers;
• digestive vacuoles.

Digestive system

A unicellular organism can actively reproduce only in moisture; in the dry habitat of the amoeba, nutrition and reproduction are impossible.

Respiratory system and response to irritation

Amoeba proteus

Amoeba division

The most favorable living environment is found in the reservoir and human body . Under these conditions, the amoeba multiplies quickly, actively feeds on bacteria in bodies of water and gradually destroys the tissues of the organs of its permanent host, which is a person.

Amoeba reproduces asexually. Asexual reproduction involves cell division and the formation of a new one-celled organism.

It is noted that one adult can divide several times a day. This determines the greatest danger for a person who suffers from amoebiasis.

That is why, at the first symptoms of the disease, doctors strongly recommend seeking help from a specialist rather than starting self-medication. Incorrectly selected medications can actually cause more harm to the patient than good.

The common amoeba (kingdom Animals, subkingdom Protozoa) has another name - Proteus, and is a representative of the class Sarcodidae free-living. It has a primitive structure and organization, moves with the help of temporary growths of cytoplasm, more often called pseudopods. Proteus consists of only one cell, but this cell is a complete independent organism.

Habitat

The structure of an ordinary amoeba

The common amoeba is an organism consisting of one cell leading an independent existence. The body of the amoeba is a semi-liquid lump, 0.2-0.7 mm in size. Large individuals can be seen not only through a microscope, but also with a regular magnifying glass. The entire surface of the body is covered with cytoplasm, which covers the nucleus pulposus. During movement, the cytoplasm constantly changes its shape. Stretching out in one direction or the other, the cell forms processes, thanks to which it moves and feeds. Can push off algae and other objects using pseudopods. So, in order to move, the amoeba extends the pseudopod in the desired direction and then flows into it. The movement speed is about 10 mm per hour.

Proteus does not have a skeleton, which allows it to take any shape and change it as needed. The respiration of the common amoeba is carried out over the entire surface of the body; there is no special organ responsible for the supply of oxygen. During movement and feeding, the amoeba captures a lot of water. Excess of this fluid is released using a contractile vacuole, which bursts, expelling water, and then forms again. The common amoeba has no special sensory organs. But she tries to hide from the direct sunlight, sensitive to mechanical irritants and some chemicals.

Nutrition

Proteus feeds on single-celled algae, rotting debris, bacteria and other small organisms, which it captures with its pseudopods and pulls into itself so that the food ends up inside the body. Here a special vacuole is immediately formed, into which digestive juice is released. Amoeba vulgaris can feed anywhere in the cell. Several pseudopods can simultaneously capture food, then digestion of food occurs in several parts of the amoeba at once. Nutrients enter the cytoplasm and go into the construction of the amoeba’s body. Particles of bacteria or algae are digested, and the remaining waste is immediately removed outside. The common amoeba is capable of throwing out unnecessary substances in any part of its body.

Reproduction

Reproduction of the common amoeba occurs by dividing one organism into two. When the cell has grown sufficiently, a second nucleus is formed. This serves as a signal for division. The amoeba stretches out, and the nuclei disperse on opposite sides. A constriction appears approximately in the middle. Then the cytoplasm in this place bursts, so two separate organisms arise. Each of them contains a core. The contractile vacuole remains in one of the amoebas, and a new one appears in the other. During the day, the amoeba can divide several times. Reproduction occurs in the warm season.

Cyst formation

With the onset of cold weather, the amoeba stops feeding. Its pseudopods are retracted into the body, which takes the shape of a ball. A special layer is formed on the entire surface protective film- cyst (protein origin). Inside the cyst, the organism is in hibernation and does not dry out or freeze. The amoeba remains in this state until favorable conditions occur. When a reservoir dries out, cysts can be carried by the wind to long distances. In this way, amoebas spread to other bodies of water. When warmth and suitable humidity arrive, the amoeba leaves the cyst, releases its pseudopods and begins to feed and reproduce.

Place of amoeba in wildlife

The simplest organisms are a necessary link in any ecosystem. The importance of the common amoeba lies in its ability to regulate the number of bacteria and pathogens on which it feeds. The simplest single-celled organisms eat rotting organic remains, maintaining the biological balance of water bodies. In addition, the common amoeba is food for small fish, crustaceans, and insects. And those, in turn, are eaten more big fish and freshwater animals. These same simple organisms serve as objects scientific research. Large clusters single-celled organisms, including the common amoeba, participated in the formation of limestone and chalk deposits.

Amoeba dysentery

There are several varieties of protozoan amoebas. The most dangerous for humans is the dysenteric amoeba. It differs from the ordinary one in having shorter pseudopods. Once in the human body, dysenteric amoeba settles in the intestines, feeds on blood and tissues, forms ulcers and causes intestinal dysentery.

The subkingdom Unicellular includes animals whose body consists of only one cell, mostly microscopic in size, but with all the functions inherent in the body. Physiologically, this cell represents a whole independent organism.

The two main components of the unicellular body are the cytoplasm and the nucleus (one or more). The cytoplasm is surrounded by an outer membrane. It has two layers: the outer (lighter and denser) - ectoplasm - and the inner - endoplasm. The endoplasm contains cellular organelles: mitochondria, endoplasmic reticulum, ribosomes, elements of the Golgi apparatus, various supporting and contractile fibers, contractile and digestive vacuoles, etc.

Habitat and external structure of the common amoeba

The simplest lives in water. This could be lake water, a drop of dew, soil moisture, or even water inside us. The surface of their body is very delicate and dries out instantly without water. Externally, the amoeba looks like a grayish gelatinous lump (0.2-05 mm), which does not have a permanent shape.

Movement

The amoeba “flows” along the bottom. On the body, outgrowths that change their shape are constantly formed - pseudopodia (pseudopods). Cytoplasm gradually flows into one of these protrusions, the false stalk attaches to the substrate at several points, and movement occurs.

Internal structure

Internal structure of amoeba

Nutrition

While moving, the amoeba encounters unicellular algae, bacteria, and small unicellular organisms, “flows around” them and includes them in the cytoplasm, forming a digestive vacuole.

Amoeba nutrition

Enzymes that break down proteins, carbohydrates and lipids enter the digestive vacuole, and intracellular digestion occurs. Food is digested and absorbed into the cytoplasm. The method of capturing food using false legs is called phagocytosis.

Breath

Oxygen is used for cellular respiration. When it becomes less than in the external environment, new molecules pass into the cell.

Amoeba breathing

Carbon dioxide molecules and harmful substances, accumulated as a result of life activity, on the contrary, come out.

Selection

The digestive vacuole approaches the cell membrane and opens outwards to release undigested residues to the outside anywhere in the body. The liquid enters the amoeba's body through the thin tube-like channels that are formed, by pinocytosis. By pumping out excess water contractile vacuoles are removed from the body. They gradually fill, and every 5-10 minutes they sharply contract and push the water out. Vacuoles can appear in any part of the cell.

Reproduction

Amoebas reproduce only asexually.

Amoeba reproduction

The grown amoeba begins to reproduce. It occurs through cell division. Before cell division, the nucleus doubles so that each daughter cell receives its own copy. hereditary information(1). Reproduction begins with a change in the nucleus. It stretches out (2), and then gradually lengthens (3.4) and is pulled in the middle. A transverse groove is divided into two halves, which diverge in different sides- two new nuclei are formed. The body of the amoeba is divided into two parts by a constriction and two new amoebas are formed. Each of them contains one core (5). During division, the formation of missing organelles occurs.

During the day, division can be repeated several times.

Asexual reproduction- simple and quick way increase the number of your descendants. This method of reproduction is no different from cell division during the growth of the body of a multicellular organism. The difference is that the daughter cells of a unicellular organism diverge as independent cells.

Reaction to irritation

Amoeba has irritability - the ability to sense and respond to signals from external environment. Crawling onto objects, it distinguishes edible from inedible and grabs them with its pseudopods. She crawls away and hides from bright light (1),

mechanical irritations and increased concentrations of substances harmful to it (2).

This behavior, consisting of movement towards or away from a stimulus, is called taxis.

Sexual process

Absent.

Experiencing adverse conditions

A single-celled animal is very sensitive to environmental changes.

In no favorable conditions(when the reservoir dries out, in the cold season) amoebas retract pseudopodia. A significant amount of water and substances are released from the cytoplasm onto the surface of the body, which form a durable double shell. There is a transition to a resting state - a cyst (1). In the cyst, life processes are suspended.

Cysts carried by the wind contribute to the spread of the amoeba.

When favorable conditions occur, the amoeba leaves the cyst shell. It releases pseudopodia and enters an active state (2-3).

Another form of protection is the ability to regenerate (recovery). A damaged cell can complete its destroyed part, but only if the nucleus is preserved, since all information about the structure is stored there.

Life cycle of amoeba

The life cycle of an amoeba is simple. The cell grows, develops (1) and divides asexually (2). In poor conditions, any organism can “temporarily die” - turn into a cyst (3). When conditions improve, it “comes back to life” and multiplies vigorously.

As a rule, dysenteric amoeba is localized in gastrointestinal tract. This bacterium is small in size (up to 30 micrometers), with high activity and mobility. Amoeba dysentery is common in all corners of the planet Earth and, depending on the habitat, infection on average reaches up to 20% of the entire population.

Infection with dysentery amoeba may not always be accompanied by pronounced symptoms, since it often leads moderate vital activity in the gastrointestinal tract, feeding on bacteria and not causing pathological processes.

Under certain factors, the amoeba can change its behavior and begin to actively invade the intestinal walls, causing ulcerations and abscesses. Bacteria that have penetrated into the tissue begin to feed on red red blood cells and, if treatment is not started in time, the disease becomes chronic, depletes the human body and leads to death.

Amoeba proteus

This bacterium is also called the common amoeba or rhizopod. The microorganism is relatively large – up to 0.5 millimeters in length. Lives this type amoebas in fresh water, as a rule, in closed reservoirs - swamps, rotting ponds and is distributed throughout the world. It reproduces by dividing the mother cell into daughter cells.

Intestinal form

Iodameba Bünchli

Dwarf amoeba

Hartmann's amoeba

This microorganism is not capable of causing any pathological manifestations in the human body. Outwardly, it resembles the dysentery variety, but reaches a much smaller size. At the vegetative stage of development maximum length Hartmann's amoeba reaches 12, and the size of the cysts is 10 micrometers.

Oral amoeba

Dienthamoeba

Infection occurs during direct contact of a person with contaminated water, while the pathogenic microorganism penetrates the nasal sinuses, then into the olfactory nerve and into the brain, spreading throughout all its parts. The amoeba, which devours the brain, actively multiplies, causing necrosis and hemorrhage in the brain. This disease almost always ends in death.

Types of amoebiasis

Amebiasis has several forms of development, which differ in severity and specific symptoms: asymptomatic and manifest, including intestinal and extraintestinal forms. Intestinal amebiasis is characterized by dysentery and amoebic colitis, and extraintestinal amebiasis is characterized by amoebic lesions of organs other than the digestive tract.

Intestinal

This form of amoebiasis is caused mainly by dysenteric amoeba. In the aggressive stage of development, it penetrates the intestinal walls, causing the development of ulcers, erosions and suppuration. An infected person has an increased urge to defecate, pain in the lower abdomen, and an admixture of mucus and blood in the stool.

Asymptomatic form

Dysenteric amoeba can live in the lower intestines without manifesting itself or causing pathological processes. After infection incubation period amoebiasis lasts about 14 days. During this time, the bacterium quietly feeds on intestinal bacteria without affecting the mucous membranes and walls. At this time, a person, unaware of his infection, becomes a carrier of the infection.

Acute

The amoeba, under the influence of certain factors, acquires an aggressive form, penetrating the intestines and damaging its walls. Pronounced symptoms of infection appear: bowel movements become more frequent up to 20 times a day, they are often false and painful, the stool becomes liquid and contains blood. The patient complains of paroxysmal pain in the lower abdomen, poor health and loss of appetite.

Lightning fast

In case of immunodeficiency, the incubation period of amoebiasis lasts no more than 2 days, the symptoms are immediately pronounced, since microorganisms multiply at lightning speed. The fulminant form of amebiasis often occurs after pregnancy, since the mother’s body is weakened by childbirth and lactation. This form of the disease often leads to severe complications, so if symptoms appear, you should immediately visit a doctor and begin the necessary treatment.

Clinical picture

Chief physician of Moscow City Hospital No. 62. Anatoly Nakhimovich Makhson
Medical practice: more than 40 years.

Unfortunately, in Russia and the CIS countries, pharmaceutical corporations sell expensive medications that only relieve symptoms, thereby hooking people on one drug or another. This is why in these countries there is such a high percentage of infections and so many people suffer from “non-working” drugs.

Chronic form

If no action is taken during the acute form of amoebiasis, it will last up to 2 months, and then the symptoms will gradually subside on their own. But this does not mean that the disease has completely cured itself - it has simply become chronic and after some time the exacerbation phase will begin again. During the period of remission, the person remains a carrier of cysts and poses a threat to surrounding healthy people.

Extraintestinal

If signs of amoebiasis develop, you should immediately consult a doctor and take a blood test. necessary tests, and if the results are positive, start treatment immediately.

Types of amoebas

Representatives of amoebas are divided into 3 main types, similar in their species characteristics, namely:

• Intestinal.
• Dysenteric.
• Amoeba Proteus.

Amoeba Proteus has a body size not exceeding 5 mm. The microorganism lives exclusively in water (with low salt concentration) and feeds on algae.

Intestinal. It lives only in the rectum and can feed on animal and plant foods.

Dysenteric. It settles in the human intestines and provokes the appearance of amoebiasis. It has several life forms, such as:

• Cyst.
• Vegetative (small).
• Tissue (large) vegetative.

Non-pathogenic amoebas

Amoebas that are not included in the pathogenic group have also been studied. These include:

Consequently, today you can become infected with any type of amoeba at any time, and in most cases the infection does not go away without leaving a trace. That is why, in order to avoid undesirable consequences, it is necessary to: adhere to the rules of personal hygiene and conduct thorough heat treatment of food.

Each type of bacteria has the following systems necessary for full life activity:

• Reproductive.
• Respiratory.
• Digestive.

The cytoplasm is surrounded by a membrane consisting of 3 layers: inner, outer and middle.

• Digestive vacuoles.
• Ribosomes.
• Contractile and supporting fibers.

Characteristics of the digestive system

The digestive system is an integral structural part of the amoeba. The food for them is usually bacteria located around the microorganism itself.

The bacterium feeds as follows:

• Moving in space, it encounters bacteria or other small single-celled organisms and algae.
• Captures food with pseudopods by phagocytosis.
• Flows around her and absorbs her body.

The resulting vacuole penetrates into the cytoplasm and is digested there. Depending on their habitat, amoebas can feed exclusively on small organisms (this applies to developing individuals), and adults can also consume algae.

It is important that the amoeba has a delicate body and can feed and reproduce exclusively in conditions high humidity. Once in a dry environment, it dries out and dies!

Respiratory system

The respiratory organs are located along the entire perimeter of the body of the bacterium. Inhaling air, the amoeba processes it and releases carbon dioxide, which is harmful to human body. As a result, the patient begins to suffer from severe intoxication caused by gas poisoning.

Amoeba reaction to irritation

While conducting research, scientists noticed that the amoeba reacts to the following factors:

• Changes in the environment.
• Bright light.

Drought response

If the body of water in which the microorganism lived dries up, the bacterium begins to defend itself. Then it secretes a liquid that covers the entire body and the bacterium becomes cystic. It can live in this form until it again finds itself in a humid environment and becomes active.

At this stage, the activity of the bacterium stops. Amoeba does not divide and does not feed. The carrier of cysts is the wind. It spreads them very quickly, as a result of which other bodies of water become infected.

Where does amoeba live?

• Inside the human body.
• In reservoirs.
• In the air (in the form of a cyst).

Reproduction