The common amoeba is a cell in appearance and is directly related to the type of protozoa, to the class of rhizomes, or they are also called Sarcodaceae. They have pseudopods, which are organs with which they move and capture food. The cell does not have a dense membrane, and therefore the amoeba can easily change its shape. The outer covering is a very thin cytoplasmic membrane.
Amoeba ordinary structure.
Amoeba has a very simple structure. One of the simplest living creatures. Has no skeleton. The common amoeba lives at the bottom of various reservoirs, in silt. There is one thing: in bodies of water only fresh water: a pond, a ditch, etc. If you look at it, you will notice that this gray transparent lump does not have a permanent shape. The name of this creature translates as “changeable.” Pseudopods are constantly forming on the cell body, due to the fact that the cytoplasm flows back and forth. The size of the lump can be at least 0.2 millimeters and, at most, 0.7 millimeters. Organelles - pseudopods contribute to the movement of this tiny creature. The movement is very slow, it resembles the flow of thick mucus. During its movement, the amoeba encounters different single-celled organisms, such as algae, bacteria. It flows around them and, as it were, absorbs them with its own cytoplasm, and a digestive vacuole is formed.
The common amoeba secretes specific enzymes in its cytoplasm that digest food. The process of intracellular digestion occurs. Digested foods in liquid form enter the cytoplasm itself, and undigested food remains are thrown away. This method of food capture is called phagocytosis. The body of the amoeba has thin channels through which fluid enters the cell body. This process is called pinocytosis. There is one vacuole that throws excess liquid products out. It's called Eliminate excess every five minutes. The endoplasm contains a nucleus. Reproduction occurs as follows: the cell divides in half, that is, asexually.
How an amoeba protects itself from adverse external influences.
Common amoeba and dysenteric amoeba are Move with the help of organelles-psepododes, belong to the rhizopods;
The class of rhizomes resembles algae, which indicates their relationship;
It feeds on what it gets from other plants, or from others, which is what distinguishes amoebas from algae.
Amoeba is, although the simplest, a whole organism capable of leading an independent existence.
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 for breathing, and external environment release carbon dioxide.
Species
Under unfavorable conditions (temperature fluctuations, drying out of ponds, air currents) 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 consists 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:
- Intestinal amebiasis (dysenteric amoebic colitis, amoebic dysentery). Characteristic symptoms: profuse diarrhea streaked with blood, mucus and pus. As the disease progresses, the negative manifestations in the form of increased body temperature, chills, vomiting, loss of appetite. During defecation, cramping pain in the lower abdomen is possible, which is less pronounced in a calm state.
- 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 appears already on late stages diseases 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 the 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 severe complications in the liver, lungs and even the brain. Prevention and timely contact with a specialist make it possible to prevent dangerous consequences.
The structure of sarcodes using an example
amoeba protea - Amoeba proteus
Body shape, differentiation of protoplasm and movement of amoeba; vacuoles and nucleus
Work 1. Body shape, differentiation of protoplasm and movement of the amoeba. These animals received the name “naked amoebas” due to their lack of a shell; They also don’t have a shell. Living protoplasm constantly slowly flows in one direction or another, as a result of which the shape of the individual’s body changes all the time.
In amoeba, layer-by-layer differentiation of the cytoplasm can be clearly seen. Outer layer, ectoplasm, glassy: transparent, structureless, homogeneous in its internal structure; this is a viscous compacted layer of protoplasm; it covers the entire body of the amoeba like a cover, performing, in particular, the function of protection from external influences (Fig. 4). The inner layer, endoplasm, is darker, liquid, with a granular structure; The endoplasm is in a state of constant fluidity. Two layers of protoplasm are two states of the same colloidal substance, passing from one to another; There is no boundary structure between the layers.
In one of the areas of the amoeba's body, protoplasm flows from the center to the periphery, forming a pseudopod, or pseudopodium; at the same time, in the opposite area, the protoplasm flows in the opposite direction, towards the central part of the body, and the other pseudopodia is retracted. So all the protoplasm flows in a certain direction, and the amoeba slowly moves from one place to another. This movement of the animal with the help of temporary formations, specific to sarcodes, is called amoeboid. At the anterior end of the pseudopodium, the endoplasm, reaching the surface of the body, turns into ectoplasm; when the pseudopodia is retracted, the ectoplasm inside the body turns into endoplasm. In progress
The layer-by-layer differentiation of protoplasm described above is especially clear in the formation of pseudopodia.
The number of pseudopodia in an amoeba depends on the species to which it belongs (Fig. 4). U Amoeba limax - single pseudopodium on the side of the body in the direction of movement. U A. proteus there are several of them, up to a dozen. The shape of the pseudopodia is different. However, both the number and shape of pseudopodia depend to a large extent on external conditions.
In terms of the function it performs, the pseudopodium is similar to the organs of movement of multicellular animals, but in structure it differs significantly from them, since it is formed not by many cells, but only by a section of a unicellular body; This kind of adaptation to perform functions in protozoa is called, in contrast to organs, organelles.
Rice. 4. Free-living amoebas. A- structure diagram Amoeba proteus; B- Amoeba Umax; IN- A. radiosa, with a pseudopodia shape characteristic of each species:
1
- pseudopodia; 2
- ectoplasm; 3 - endoplasm; 4
- food vacuole; 5
- contractile vacuole; 6 -
core
Work progress. Sarcodidae are studied mainly on living material. The absence of live animals is only partially compensated by the use of ready-made micropreparations.
Make a temporary preparation from a drop of culture; equip the cover glass with wax “legs”. Under a microscope at low magnification, find the amoeba; observe it calmly and for a long time in a slightly shaded field at high magnification, avoiding jolts and shaking of the specimen. When observing a living amoeba, consider: a) indefinite form bodies; sketch the outlines
bodies at four to five successive stages of change in body shape; b) different layers of protoplasm; indicate them in the figure and note the function of ectoplasm; c) trace the process of formation (or leakage) of pseudopodium and its disappearance (retraction); Draw a picture of the number and shape of pseudopodia that approximately correspond to the observations, and note their function.
In the absence of amoebas, the task can be completed on arcella.
Work 2. Vacuoles and nucleus. Amoeba feeds on small algae, bacteria, etc., which it captures with pseudopodia. Moving from place to place, it encounters food objects and flows around them until it is completely surrounded. Food with a small amount of water ends up inside the protoplasm. This is how the food, or digestive, vacuole is formed; Enzymes flow here from the protoplasm surrounding the vacuole, under the influence of which digestion occurs. A food vacuole is formed in any part of the amoeba's body that comes into contact with food. Digested food in dissolved form directly passes into protoplasm and is assimilated. Indigestible residues are thrown out through the surface of the body in any place where the food vacuole approaches, after which it disappears, since it does not have its own wall. Consequently, eating and removing indigestible residues, i.e. defecation, not confined to a specific area of the body.
In terms of its function, the digestive organelle - the food vacuole - is similar to the digestive system of multicellular animals.
Contractile, or pulsating, i.e. periodically appearing and disappearing, the vacuole is represented in the amoeba as a vesicle under the ectoplasm (see Fig. 4). As the bubble fills, it slowly increases in size; when it reaches its maximum size, it bursts and the contents pour out through the ectoplasm. The rate of vacuole pulsation depends on external conditions (temperature, etc.). At room temperature, it takes a few minutes to fill.
The contractile, or pulsating, vacuole in the amoeba does not have a permanent location. Since the concentration of salts and, accordingly, the osmotic pressure in the protoplasm is higher than in fresh water, water constantly penetrates into the body of the amoeba from the outside; its excess is removed outside (pumped out)
by the action of a pulsating vacuole, thereby fulfilling the role osmoregulatory apparatus.
The final products of the chemical decomposition of proteins and carbohydrates, i.e., dissimilation products, enter the contractile vacuole along with water from the protoplasm and are excreted. The contractile vacuole therefore serves as an organelle of excretion, like the kidneys, organs of higher animals with the same function. With water through the contractile vacuole, in particular, carbon dioxide dissolved in it is removed; This is how breathing is partially carried out, mainly flowing through the entire surface of the body.
Work progress. 1. Continuing to observe the amoeba at high magnification of the microscope: a) find food vacuoles and excretory vacuoles; mark them in the picture; b) monitor the filling and disappearance of the vacuole. 2. In a living amoeba, the nucleus is difficult to detect. Examine it on a special pre-prepared microslide, where the amoebas are killed (fixed) and stained; complete the core into the overall drawing.
Amoeba is a representative of the simplest single-celled animals. A free-living protozoan cell is capable of moving independently, feeding, defending itself from enemies, and surviving in an unfavorable environment.
As part of the subclass “Rhizopods” they belong to the class “Sarcodae”.
The rhizome is represented by a wide variety of forms, among which three orders are distinguished:
- naked;
- shell;
- foraminifera.
The presence of a unifying feature - pseudopods - allows testates and foraminifera to move in the same way as an amoeba moves.
In nature, the greatest species diversity is observed among the marine inhabitants of foraminifera - over a thousand species. There are significantly fewer shell forms of rhizomes - several hundred; they are often found in water, swamps, and mosses.
Radiolarians with a skeleton are sometimes classified as marine amoebae, although according to classification they belong to a different subclass of sarcodidae.
Of interest to medical practice are naked (ordinary) amoebas, which have no skeleton or shells in their structure. They live naked in both fresh and salt waters. The primitive organization of this organism is reflected in its species name “protea” (“protea” means simple, although there is an interpretation of this name that refers to ancient Greek god Proteus).
There are more than 100 species of Proteas, among them 6 species found in different parts human body:
- in the oral cavity;
- in the small and large intestine;
- in the abdominal organs;
- in the lungs.
All Proteas consist of one cell, the body of which is covered with a thin cytoplasmic membrane. The membrane protects the dense, transparent ectoplasm, behind which lies the jelly-like endoplasm. The endoplasm contains the bulk of the amoeba, including the vesicular nucleus. There is usually one nucleus, but there are also multinucleated species of organisms.
Proteas breathe with their whole body; waste products can be removed through the surface of the body, as well as through a specially formed vacuole.
The sizes of the common amoeba vary from 10 microns to 3 mm.
Protozoa do not have sense organs, but they are able to hide from sunlight, sensitive to chemical irritants and mechanical stress.
When unfavorable living conditions arise, proteas form a cyst: the shape of the amoeba is rounded, and a protective shell is formed on the surface. Processes inside the cell slow down until favorable times arrive.
Features allow an animal organism to form cytoplasmic projections that have different names:
- pseudopodia;
- rhizomes;
- pseudopods.
Protean pseudopodia are in continuous motion, changing shape, branching, disappearing and forming again. The number of pseudopodia is not constant, it can reach 10 or more.
Travel and food
The rhizomes ensure the movement of a single-celled amoeba and the capture of detected food. Regardless of the habitat, the amoeboid movement consists of the protrusion of the rhizome in a certain direction and the subsequent flow of cytoplasm into the cell. Pseudopodia are then formed again in another location. There is a constant, imperceptible flow of the body in search of food. This method of movement does not allow Proteas to have a fixed body shape.
In the variety of forms taken by Proteas in movement, there are up to 8 types. The characteristics of the types are determined by the shape of the cell and the type of branching of the pseudopodia during movement.
The type of movement chosen by an animal mainly depends on the composition of the aquatic habitat, which is influenced by the content of salts, alkalis and acids.
Proteas are omnivores, feeding by phagocytosis. The food for this heterotroph can be:
- bacteria;
- unicellular algae;
- small protozoa.
The feeding process begins in motion as soon as the animal discovers potential prey nearby. The body of the protozoan forms several pseudopodia that surround the found object and form a closed cavity.
Digestive juice is released into the resulting area from the cytoplasm - a digestive vacuole is formed. After assimilation nutrients undigested food remains are thrown out.
Role in biocenoses
For billions of years, protozoa have been actively involved in the formation of the Earth’s biosphere, being a necessary consumer in the food chain of various biocenoses.
The ability of the amoeba to move independently allows it to regulate the number of bacteria and pathogens on which it feeds. Biocenoses of sewage sludge deposits, peat and marshy soils, fresh and sea waters impossible without the participation of simple organisms.
Even the pathogenic dysentery amoeba in the intestinal biocenosis does not cause harm to a healthy host organism, feeding on a variety of bacteria. And only organic damage to the intestinal mucosa allows it to move into the circulatory system and switch to feeding on red blood cells.
In natural biocenoses, protozoa serve as food for fish fry, small crustaceans, worms and hydras. These, in turn, serve as food for larger creatures. Thus, amoebas become participants in the circulation of substances.
Amoeba vulgaris (Proteus) is a species of protozoan animal from the genus Amoeba of the subclass rhizopods of the Sarcodidae class of the Sarcomastigophora type. This is a typical representative of the genus of amoebas, which is a relatively large amoeboid organism, distinctive feature which is the formation of many pseudopods (10 or more in one individual). The shape of the common amoeba when moving due to pseudopodia is very variable. Thus, pseudopods constantly change appearance, branch, disappear and form again. If the amoeba releases pseudopodia in a certain direction, it can move at speeds of up to 1.2 cm per hour. At rest, the shape of amoeba Proteus is spherical or ellipsoid. When floating freely near the surface of reservoirs, the amoeba acquires a star-shaped shape. Thus, there are floating and locomotor forms.
The habitat of this type of amoeba is fresh water bodies with stagnant water, in particular, swamps, decaying ponds, and aquariums. Amoeba Proteus is found throughout the globe.
The sizes of these organisms range from 0.2 to 0.5 mm. The structure of amoeba Proteus has characteristic features. The outer shell of the body of the common amoeba is the plasmalemma. Beneath it is the cytoplasm with organelles. The cytoplasm is divided into two parts - the outer (ectoplasm) and the inner (endoplasm). The main function of the transparent, relatively homogeneous ectoplasm is the formation of pseudopodia for food capture and movement. All organelles are contained in the dense granular endoplasm, where food is digested.
The common amoeba feeds by phagocytosis of the smallest protozoa, including ciliates, bacteria, and unicellular algae. Food is captured by pseudopodia - outgrowths of the cytoplasm of the amoeba cell. When the plasma membrane comes into contact with a food particle, a depression is formed, which turns into a bubble. There they begin to stand out intensely digestive enzymes. This is how the process of forming a digestive vacuole occurs, which then passes into the endoplasm. The amoeba obtains water by pinocytosis. In this case, an invagination like a tube is formed on the surface of the cell, through which liquid enters the amoeba’s body, then a vacuole is formed. When water is absorbed, this vacuole disappears. The release of undigested food residues occurs in any part of the body surface during the fusion of a vacuole moved from the endoplasm with the plasmalemma.
In addition to digestive vacuoles, the endoplasm of the common amoeba contains contractile vacuoles, one relatively large discoidal nucleus and inclusions (fat drops, polysaccharides, crystals). Organelles and granules in the endoplasm are found in constant movement, picked up and carried by cytoplasmic currents. In a newly formed pseudopod, the cytoplasm shifts to its edge, and in a shortened pseudopod, on the contrary, it moves deeper into the cell.
Amoeba Proteus reacts to irritation - to food particles, light, negatively - to chemicals(sodium chloride).
Amoeba vulgaris reproduces asexually by cell division in half. Before the division process begins, the amoeba stops moving. First, the nucleus divides, then the cytoplasm. There is no sexual process.