Appearance, structure and movement of the amoeba. Types and life cycle of amoeba

Amoebaordinary(lat. Amoeba proteus)

or amoeba proteus(rhizopod) - amoeboid organism, representative of the class Lobosa(lobosal amoebas). Polypodial form (characterized by the presence of numerous (up to 10 or more) pseudopodia - pseudopodia). Pseudopodia constantly change their shape, branch, disappear and reappear.

Cell structure

A. proteus is externally covered only with plasmalemma. The cytoplasm of the amoeba is clearly divided into two zones, ectoplasm and endoplasm (see below).

Ectoplasm, or hyaloplasm, lies in a thin layer directly under the plasmalemma. Optically transparent, free of any inclusions. The thickness of the hyaloplasm in different parts of the amoeba’s body is different. On the lateral surfaces and at the base of the pseudopodia this is usually a thin layer, and at the ends of the pseudopodia the layer noticeably thickens and forms the so-called hyaline cap, or cap.

Endoplasm, or granuloplasm - the internal mass of the cell. Contains all cellular organelles and inclusions. When observing a moving amoeba, a difference in the movement of the cytoplasm is noticeable. The hyaloplasm and peripheral portions of the granuloplasm remain practically motionless, while its central part is in continuous motion; cytoplasmic currents with organelles and granules involved in them are clearly visible. In a growing pseudopodia, the cytoplasm moves to its end, and from shortening ones - to the central part of the cell. The mechanism of hyaloplasm movement is closely related to the process of transition of the cytoplasm from a sol to a gel state and changes in the cytoskeleton.

Nutrition

Amoeba Proteus feeds by phagocytosis, absorbing bacteria, single-celled algae and small protozoa. The formation of pseudopodia underlies food capture. On the surface of the amoeba’s body, contact occurs between the plasmalemma and the food particle, and a “food cup” is formed in this area. Its walls close, and digestive enzymes begin to flow into this area (with the help of lysosomes). Thus, a digestive vacuole is formed. Then it passes into the central part of the cell, where it is picked up by cytoplasmic currents. In addition to phagocytosis, amoeba is characterized pinocytosis- swallowing liquid. In this case, an invagination in the form of a tube is formed on the surface of the cell, through which a drop of liquid enters the cytoplasm. The forming vacuole with liquid is detached from the tube. After the liquid is absorbed, the vacuole disappears.

Defecation

Endocytosis (excretion). The vacuole with undigested food remains approaches the surface of the cell and merges with the membrane, thus throwing the contents out.

Osmoregulation

A pulsating contractile vacuole is periodically formed in the cell - a vacuole containing excess water and removing it out.

Reproduction

Only agamic, binary fission. Before division, the amoeba stops crawling, its dictyosomes, Golgi apparatus and contractile vacuole disappear. First, the nucleus divides, then cytokinesis occurs. The sexual process is not described.

Causes indigestion and colitis (bloody diarrhea).

Among the simplest organisms, the amoeba is considered the most primitive. The bacterium has microscopic dimensions and is a single-celled creature.

Amoeba is the simplest single-celled creature

Amoeba - what is it?

Amoeba (rhizopod)- the lowest category of living beings. What is it - a bacterium or an animal? The microorganism is one of the simplest single-celled animals, has tiny dimensions (from 0.2 to 0.5 mm), and the body shape changes all the time depending on external conditions. Single-celled creatures, like more complex animals, use oxygen to breathe and release carbon dioxide into the external environment.

Kinds

Under unfavorable conditions (temperature fluctuations, drying out of ponds, air currents) it goes into sleep mode, transforming into a cyst

Amoebas enter the human or animal body in the form of a cyst, which is protected by a durable two-layer shell. Infection occurs through food (poorly washed fruits and vegetables), contaminated water, and dirty hands.

Structure

The amoeba does not have a skeleton, a formed mouth, lungs or gills.

Its structure is made up of organelles:

• large core;
• cytoplasm, clearly divided into two zones - ectoplasm and endoplasm;
• pseudopodia (false legs with which the cell moves);
• digestive vacuole;
• contractile vacuole (removes excess water and food from the amoeba’s body).

What an amoeba looks like and what it consists of is shown in the photo.

Amoeba has a simple structure

Nutrition

The rhizome feeds using pseudopodia. The process of capturing solid food is called phagocytosis. Capturing food is one of the main functions of the false legs: they grasp edible particles, which helps the latter enter the nutritional vacuole, where they are enveloped by a membrane. Digestion gradually occurs, the excess of which leaves the contracting vacuole during the movement of the amoeba.

The process of food capture by amoeba

Reproduction

Amoebas can only reproduce asexually. Having reached maturity, the cell begins division, which results in 2 daughter organisms.

How they reproduce:

• change in the core (first it stretches, then lengthens, as a result of which it is pulled in the middle);
• division of the nucleus into two halves (formation of two independent nuclei);
• division of the amoeba itself into two new cells, each of which has its own nucleus.

Amoebas reproduce asexually

During the appearance of a daughter microorganism, the formation of organelles missing for the new cell occurs. In 24 hours, an amoeba can undergo the process of binary fission several times.

Life cycle

Amoeba has a simple life cycle. In a favorable environment, cells develop, grow and divide asexually. When living conditions worsen, amoebas “freeze,” thereby forming cysts. When microorganisms enter the human body, animal body, water bodies or moist soil, they come to life, are released from the protective shell and begin to actively multiply.

When environmental conditions worsen, amoebas become covered with a protective shell (cyst)

Symptoms of amoebiasis

Signs of amoebiasis largely depend on the type of disease:

1. Intestinal amebiasis (dysenteric amoebic colitis, amoebic dysentery). Characteristic symptoms: profuse diarrhea streaked with blood, mucus and pus. As the disease progresses, negative manifestations increase in the form of increased body temperature, chills, vomiting, and loss of appetite. During defecation, cramping pain in the lower abdomen is possible, which is less pronounced in a calm state.
2. Extraintestinal type of disease - occurs as a complication of intestinal amebiasis. Most often it affects the liver (abscess or amoebic hepatitis). Symptoms: enlargement of the affected organ, pain in the right hypochondrium, the appearance of jaundice, high temperature (up to 40 degrees).

When the liver is damaged by amoebas, pain appears in the right hypochondrium

Amoebiasis has a mild course (fever, diarrhea, yellowness of the skin) and manifests itself already in the later stages of the disease in the form of a breakthrough of purulent formations (peritonitis). This threatens to damage the lungs, brain, and genitourinary system.

Diagnostics

The diagnosis of amoebiasis is based on 2 main methods:

• bacteriological analysis of biological material (cysts are looked for in feces);
• endoscopic examination of the rectum (detection of the degree of damage to the intestinal mucosa).

Only after confirming the diagnosis, the specialist prescribes the necessary treatment, taking into account all the features and severity of the disease.

Endoscopic examination is used to determine the extent of damage to the rectum

Treatment of amoebiasis

Drugs that have a detrimental effect on amoebas are divided into 2 main groups:

• contact (luminal) - Clefamide, Paromomycin, Etofamide - are used for asymptomatic amoebiasis, as well as for the prevention of relapses;
• tissue - Tinidazole, Ornidazole, Metronidazole - prescribed for intestinal amebiasis, as well as in the treatment of abscesses in the liver, lungs, and brain.

Intestinal disease caused by amoebas responds well to treatment and is almost completely cured in the early stages of the pathology.

Metronidazole helps with intestinal amebiasis

Prevention

Infection with protozoa can be prevented by following simple preventive measures:

• use only boiled water (boil for at least 10 minutes);
• Wash vegetables and fruits well before use;
• make sure that flies do not land on food (cover with protective film);
• adhere to the rules of personal hygiene (wash hands after visiting the toilet, before eating, after visiting public places and walking outside);
• Do not fertilize garden beds with human feces.

Amoebas are the simplest animals that consist of a single cell. Among primitive microorganisms there is a dangerous species - dysenteric amoeba (not to be confused with the causative agents of malaria), which causes a dangerous intestinal disease amoebiasis. If the pathology is not detected in time, it can lead to serious complications in the liver, lungs and even the brain. Prevention and timely contact with a specialist make it possible to prevent dangerous consequences.

Amoeba vulgaris is a type of protozoan eukaryotic creature, a typical representative of the genus Amoeba.

Taxonomy. The species of common amoeba belongs to the kingdom - Animals, phylum - Amoebozoa. Amoebas are united in the class Lobosa and order - Amoebida, family - Amoebidae, genus - Amoeba.

Characteristic processes. Although amoebas are simple, single-celled creatures that do not have any organs, they possess all vital processes. They are able to move, get food, reproduce, absorb oxygen, and remove metabolic products.

Structure

The common amoeba is a unicellular animal, the body shape is uncertain and changes due to the constant movement of the pseudopods. The dimensions do not exceed half a millimeter, and the outside of its body is surrounded by a membrane - plasmalem. Inside there is cytoplasm with structural elements. Cytoplasm is a heterogeneous mass, where two parts are distinguished:

• External - ectoplasm;
• internal, with a granular structure - endoplasm, where all intracellular organelles are concentrated.

The common amoeba has a large nucleus, which is located approximately in the center of the animal's body. It has nuclear sap, chromatin and is covered with a membrane with numerous pores.

Under a microscope it can be seen that the common amoeba forms pseudopodia into which the cytoplasm of the animal is poured. At the moment of pseudopodia formation, endoplasm rushes into it, which in the peripheral areas becomes denser and turns into ectoplasm. At this time, on the opposite part of the body, ectoplasm partially transforms into endoplasm. Thus, the formation of pseudopodia is based on the reversible phenomenon of the transformation of ectoplasm into endoplasm and vice versa.

Breath

The amoeba receives O 2 from water, which diffuses into the internal cavity through the outer integument. The whole body participates in the respiratory act. Oxygen entering the cytoplasm is necessary to break down nutrients into simple components that Amoeba proteus can digest, and also to obtain energy.

Habitat

Inhabits fresh water in ditches, small ponds and swamps. Can also live in aquariums. Amoeba vulgaris culture can be easily propagated in the laboratory. It is one of the large free-living amoebas, reaching 50 microns in diameter and visible to the naked eye.

Nutrition

The common amoeba moves with the help of pseudopods. She covers one centimeter in five minutes. While moving, amoebas encounter various small objects: unicellular algae, bacteria, small protozoa, etc. If the object is small enough, the amoeba flows around it from all sides and it, along with a small amount of liquid, ends up inside the cytoplasm of the protozoa.

The process of absorption of solid food by the common amoeba is called phagocytosis. Thus, digestive vacuoles are formed in the endoplasm, into which digestive enzymes enter from the endoplasm and intracellular digestion occurs. Liquid digestion products penetrate the endoplasm, a vacuole with undigested food remains approaches the surface of the body and is thrown out.

In addition to digestive vacuoles, the body of amoebas also contains a so-called contractile, or pulsating, vacuole. This is a bubble of watery liquid that periodically grows, and when it reaches a certain volume, it bursts, emptying its contents out.

The main function of the contractile vacuole is to regulate osmotic pressure inside the protozoan body. Due to the fact that the concentration of substances in the cytoplasm of the amoeba is higher than in fresh water, a difference in osmotic pressure is created inside and outside the body of the protozoa. Therefore, fresh water penetrates the amoeba’s body, but its amount remains within the physiological norm, since the pulsating vacuole “pumps out” excess water from the body. This function of vacuoles is confirmed by their presence only in freshwater protozoa. In marine animals it is either absent or reduced very rarely.

In addition to the osmoregulatory function, the contractile vacuole partially performs an excretory function, removing metabolic products along with water into the environment. However, the main function of excretion is carried out directly through the outer membrane. The contractile vacuole probably plays a certain role in the process of respiration, since water penetrating into the cytoplasm as a result of osmosis carries dissolved oxygen.

Reproduction

Amoebas are characterized by asexual reproduction, carried out by dividing in two. This process begins with mitotic division of the nucleus, which lengthens longitudinally and is separated by a septum into 2 independent organelles. They move away and form new nuclei. The cytoplasm with the membrane is divided by a constriction. The contractile vacuole does not divide, but enters one of the newly formed amoebae; in the second, the vacuole forms independently. Amoebas reproduce quite quickly; the division process can occur several times during the day.

In the summer, amoebas grow and divide, but with the arrival of autumn cold, due to the drying up of water bodies, it is difficult to find nutrients. Therefore, the amoeba turns into a cyst, finding itself in critical conditions and becomes covered with a durable double protein shell. At the same time, cysts easily spread with the wind.

Meaning in nature and human life

Amoeba proteus is an important component of ecological systems. It regulates the number of bacterial organisms in lakes and ponds. Purifies the aquatic environment from excessive pollution. It is also an important component of food chains. Single-celled organisms are food for small fish and insects.

Scientists use the amoeba as a laboratory animal, conducting many studies on it. Amoeba not only cleans bodies of water, but once it settles in the human body, it absorbs destroyed particles of epithelial tissue of the digestive tract.

Precystic form It is considered transitional, it develops after the luminal one. Amoebas have minimal sizes, no more than 10-18 microns. They are difficult to detect due to their low content in feces.

Existing varieties of protozoa

• amoeba proteus;
• dysentery;
• intestinal

Amoeba proteus

Dysenteric amoeba

Dysenteric amoeba

Prevails exclusively in the human large intestine and water bodies. Once in the body, it causes a serious disease called amoebiasis. In its life cycle, three main stages are recorded: cyst, small vegetative and large vegetative form, tissue.

Penetration into the body occurs through the consumption of contaminated food in the form of cysts. In terms of its dimensions, it is characterized by minimal dimensions. The small vegetative form does not cause negative symptoms from the body; it settles in the lower intestines.

Intestinal amoeba

Non-pathogenic amoebas

There are certain types of amoebas that belong to the non-pathogenic class. This category includes:

Hartmann's amoeba

With a detailed study, specialists are able to make the wrong diagnosis. This is due to the lack of specific external data.

Common amoeba

Dwarf amoeba

Diagnosis is made by using Lugol's solution. A distinctive feature of the amoeba is its small size and the presence of a clearly defined shell.

Iodameba Bütschli

Dienthamoeba

When released into the environment, bacteria die or are destroyed; they are not adapted to unfavorable conditions.

Oral amoeba

It occurs in almost all people who suffer from oral diseases. In some cases, the bacterium is found in lesions of the respiratory system. Its size does not exceed 30 microns, the nuclei are almost invisible, and the movement is slow.

Penetrating into the human body, bacteria lead to serious disruptions in the functioning of the digestive system. The most common type of disease is. It comes in several varieties:

Acute form

The acute form of the disease begins spontaneously. First, a person is constantly plagued by irregular bowel movements with predominant diarrhea. Gradually, pain syndrome is added to the general clinical picture. There is a small amount of blood and mucus in the stool. If the disease develops in children, fever and vomiting are observed.

Lightning form

The fulminant form is characterized by a severe course. It is characterized by the presence of acute toxic syndrome, with serious damage to the intestinal walls. Women are predisposed to the development of pathology in the postpartum period.

In the absence of therapeutic effects, a high risk of death remains.

Protracted amoebiasis

Prolonged amebiasis is accompanied by severe intestinal motility disorders. A person often experiences constipation and diarrhea. In this case, acute pain syndrome, nausea and weakness are recorded. The patient refuses to eat.

Extraintestinal amebiasis is characterized by damage to many organs, in particular the liver.

Extraintestinal amoebiasis

A less common type of disease is extraintestinal amebiasis. It is characterized by damage to many organs, in particular the liver. Severe disorders are recorded exclusively in adults and require immediate surgical intervention.

Coping with amoebas is not so easy, due to their high resistance to adverse conditions.

In contact with

Habitat of the common amoeba

The common amoeba is found in the sludge at the bottom of ponds with polluted water. It looks like a small (0.2-0.5 mm), barely visible to the naked eye, colorless gelatinous lump, constantly changing its shape (“amoeba” means “changeable”). The details of the amoeba's structure can only be seen under a microscope.

The structure and movement of the common amoeba

The body of the amoeba consists of semi-liquid cytoplasm with a small vesicular nucleus enclosed inside it. An amoeba consists of one cell, but this cell is a whole organism leading an independent existence.
The cytoplasm of a cell is in constant motion. If the current of cytoplasm rushes to one point on the surface of the amoeba, a protrusion appears in this place on its body. It enlarges, becomes an outgrowth of the body - a pseudopod, cytoplasm flows into it, and the amoeba moves in this way. Amoeba and other protozoa capable of forming pseudopods are classified as rhizopods. They received this name due to the external resemblance of their pseudopods to plant roots.

Nutrition of amoeba vulgaris

An amoeba can simultaneously form several pseudopods, and then they surround food - bacteria, algae, and other protozoa. Digestive juice is secreted from the cytoplasm surrounding the prey. A bubble is formed - a digestive vacuole.
Digestive juice dissolves some of the substances that make up food and digests them. As a result of digestion, nutrients are formed that leak from the vacuole into the cytoplasm and go to build the body of the amoeba. Undissolved residues are thrown out anywhere in the amoeba’s body.

Dykhan not amoeba vulgaris

The amoeba breathes oxygen dissolved in water, which penetrates its cytoplasm through the entire surface of the body. With the participation of oxygen, complex food substances in the cytoplasm are decomposed into simpler ones. This releases the energy necessary for the functioning of the body.

Release of harmful substances and excess water from amoeba vulgaris

Harmful substances are removed from the amoeba's body through the surface of its body, as well as through a special vesicle - a contractile vacuole. The water surrounding the amoeba constantly penetrates the cytoplasm, diluting it. The excess of this water with harmful substances gradually fills the vacuole. From time to time, the contents of the vacuole are thrown out.
So, food, water, and oxygen enter the amoeba’s body from the environment. As a result of the life activity of the amoeba, they undergo changes. Digested food serves as material for building the body of the amoeba. Substances that are harmful to the amoeba are removed outside. The metabolism of the amoeba vulgaris occurs. Not only amoeba, but all other living organisms cannot exist without metabolism both within their body and with the environment.

Reproduction of amoeba vulgaris

The amoeba's nutrition causes its body to grow. The grown amoeba begins to reproduce. Reproduction begins with a change in the nucleus. It stretches out, is divided by a transverse groove into two halves, which diverge in different directions - two new nuclei are formed. The body of the amoeba is divided into two parts by a constriction. Each of them contains one core. The cytoplasm between both parts is torn and two new amoebas are formed. The contractile vacuole remains in one of them, but appears anew in the other. So, the amoeba reproduces by dividing in two. During the day, division can be repeated several times.

Amoeba cyst

Amoeba feeds and reproduces throughout the summer. In autumn, when cold weather sets in, the amoeba stops feeding, its body becomes rounded, and a dense protective shell is formed on its surface - a cyst is formed. The same thing happens when the pond where the amoebas live dries out. In the state of a cyst, the amoeba tolerates unfavorable living conditions. When favorable conditions occur, the amoeba leaves the cyst shell. She releases pseudopods, begins to feed and reproduce. Cysts carried by the wind contribute to the spread of amoebas.