What does freshwater amoeba eat? The structure and life of protozoa

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

Prevails exclusively in the human large intestine and water bodies. Once in the body, it causes a serious disease called amoebiasis. In her 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

Highlight certain types amoebas, which 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. Distinctive feature 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 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 organs 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, it persists high risk lethal outcome.

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.

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-cell 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. The cytoplasm is a heterogeneous mass, where 2 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, together with a small amount liquid appears inside the cytoplasm of the protozoan.

Amoeba vulgaris nutritional diagram

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, having reached a certain volume, 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. That's why 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, releasing 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 summer period over time, amoebas grow and divide, but with the arrival of autumn cold, due to the drying up of reservoirs, 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. Cleanses 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.

Habitat "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.

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 the cell is in constant movement. 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 for external resemblance pseudopods with plant roots.

Food "Ameba 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.

Breathing "Ameba 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 energy necessary for the functioning of the body.

Release of harmful substances from vital activity and excess water "Vulgar Amoeba"

Harmful substances are removed from the amoeba’s body through the surface of its body, as well as through a special vesicle - 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, from environment The amoeba's body receives food, water, and oxygen. 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. Happening metabolism of amoeba vulgaris. Not only amoeba, but all other living organisms cannot exist without metabolism both within their body and with the environment.

Reproduction of "Ameba 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 into different sides- 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.

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 advancing favorable conditions 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.

Be among single-celled creatures,

Protozoa aquatic.

Don’t ask: “What do I care?”

You know, everything comes from them.

“Single-celled, protozoa,” the poet A.S. Kushner invites the reader to be among them – these include amoebas. Let us also be among the amoebas! To do this, we will have to arm ourselves with a microscope - after all, the size of the largest amoeba does not exceed a millimeter, and more often their size is measured in micrometers (thousandths of a millimeter) - and we want to take a good look at how this creature works... not so long ago we would have said “animal” – after all, once upon a time the protozoa (including amoebas) were classified as members of the animal kingdom, and only recently they were separated into a separate kingdom - Protista, which united single-celled organisms, which in no case should be mixed with bacteria... what is the difference?

About 3 billion years ago, an event occurred on Earth before which all our great revolutions faded: among the single-celled organisms that existed then, cells appeared whose genetic apparatus was enclosed in the nucleus. This new acquisition is truly difficult to overestimate: without going into the “wild” of genetics, we can say that it made it possible to create more viable mutations. The result was not long in coming (on the scale of history, of course!): eukaryotic cells (the so-called creatures that have a cell nucleus) acquired numerous organelles, subsequently giving rise to a whole variety of species of plants, fungi, animals - right up to humans... while prokaryotes (cells lacking a nucleus) remained bacteria... What did the first eukaryotes look like?

This is probably what they looked like - like amoebas: a droplet of semi-liquid cytoplasm enclosed in a membrane (shell) - and a nucleus inside. In addition to the nucleus, inside the amoeba there is also a pulsating vesicle - a contractile vacuole, which pushes out excess fluid.

This living “droplet” is in constant motion: a small protrusion appears on the body, which turns into a long process - and the entire body of the amoeba “flows” into it to immediately produce a new process. The body of the amoeba is constantly shimmering with such temporary outgrowths - “legs” ... but, of course, these are not real “legs” in our understanding, they are called so - pseudopods, or pseudopodia.

With the help of pseudopodia, the amoeba not only moves, but also captures prey: several pseudopodia are formed, they surround a bacterium, a unicellular algae or a smaller protozoan - and now the prey is already inside the amoeba. A bubble of digestive juice forms around it - a digestive vacuole. After dissolution, part of the substances is used to build the body of the amoeba, the rest is thrown out (the amoeba does not have a special hole for this - the release occurs through the membrane).

As the amoeba feeds, it grows, and having reached a certain size, it begins to reproduce - of course, asexually (such a primitive organism cannot have sex) - by division: the amoeba stops moving, the contractile vacuole disappears; the nucleus divides, then a constriction is formed, separating the cytoplasm into two parts - and finally, the cell ruptures, forming two independent individuals of a smaller size. This is how the life of an individual amoeba ends... perhaps you can call it immortality: no corpse remains, no one died! Fortunately, amoebas do not have the consciousness to judge how identical the daughter individuals are to the one from which they were formed...

True, an amoeba is like any other living creature– you can kill... but it’s not easy! When an amoeba finds itself in an unfavorable environment for it - for example, the reservoir where it lives dries up, or cold weather sets in - the amoeba acquires a rounded shape and becomes covered with a hard shell - a cyst is formed. In this form, the amoeba will safely endure the conditions that threaten it - in order to “come to life” as soon as favorable conditions return... and in the form of such a cyst, you can easily swallow it along with water or food!

We keep talking about amoebas, but there are many types of them, and among them there are some that are dangerous to us! For example, dysentery amoeba, which can easily be “obtained” in countries with hot climates. It settles in the large intestine and can behave quietly at first, feeding on bacteria (the person is not yet sick - but is already a carrier). When it penetrates the intestinal wall, purulent ulcers form there, and when it gets into other organs with the blood, amoebas cause abscesses there... This disease is called amoebiasis, and if it is not treated, it becomes chronic, and in especially severe cases it can even lead to to death. So if you go to some tropical country, do not buy drinks and fruits from street vendors there (even ice in soft drinks may be a source of infection), do not drink unboiled water and unpasteurized dairy products, and wash and peel vegetables and fruits only yourself!

And in the 60s of the 20th century, another “enemy” from the world of amoebas was discovered in Australia - the lake amoeba, which affects nervous system. In 2007, it was encountered in the USA: six people died after the same symptoms - shooting in the neck, headache, fever, then hallucinations and changes in behavior indicating brain damage... The causative agent of the disease was lake amoeba, which lives on shallow. It is very thermophilic, and according to scientists’ forecasts, it will “raise its head” as global warming...

However, natural enemies We have no more amoebas than other living creatures... In any case, it’s worth taking a closer look at them. Did you know that if human cells are removed from the body and placed on a nutrient medium, they will release pseudopodia and begin to behave like real amoebas? Apparently, we have much more in common with amoebas than it might seem... indeed, as the poet said, “everything comes from them.”

The cytoplasm is completely surrounded by a membrane, which is divided into three layers: outer, middle and inner. The inner layer, which is called endoplasm, contains the 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.