Viruses and bacteria are tiny objects that can only be seen with a powerful microscope. Viruses and bacteria can be found anywhere on our planet, and both play an important role in evolution. Both bacteria and viruses can cause disease in plants, animals, and humans. How are they different? Having studied them more thoroughly, we can conclude that they have something in common, but also a lot of differences.

Some information about viruses

Viruses are microscopic objects, the characteristic feature of which is that their life cycle can only take place inside a living cell. Outside a living organism, viruses do not show signs of life.

A virus that is outside a living cell is called a virio. The sizes of virions fluctuate over a wide range - from 15 to 400 nm.

Virus structure

A simply arranged virus consists of capsid- a protein shell that protects the genetic material of the virus - its nucleic acid (genome). According to the classification of viruses created by Nobel laureate in physiology or medicine David Baltimore, there are seven possible variants of the viral genome:

1. Viruses with double-stranded DNA.
2. Viruses with single-stranded DNA.
3. RNA viruses whose genetic material replicates in the cytoplasm.
4. Viruses with single-stranded RNA of a positive sign (RNA (+)).
5. Viruses with single-stranded RNA of a negative sign (RNA (-)).
6. Viruses with single-stranded RNA (+), which use a special enzyme for replication - reverse transcriptase, which allows you to synthesize DNA on an RNA template.
7. Viruses with double-stranded DNA, using single-stranded RNA in the process of implementing the genetic material.

The ability of RNA to store genetic information is a unique property found only in viruses.

More complex viruses include an additional shell - supercapsid. Spiny processes formed from lipo- or glycoproteins can often be observed on the surface of the supercapsid. These processes have the ability to cause agglutination (gluing) of erythrocytes when they fall into the blood, bind to receptors on the surface of a vulnerable cell, and, subsequently, destroy its walls.

Once inside the cells and having lost unnecessary protective shells, the virus begins to realize its genetic material - to synthesize viral proteins and replicate the genome. The viral genome can be integrated into the chromosome of the affected cell by recombination, and then when the cell divides, the virus genome will double. Plant viruses have the ability to move from one cell to another.

General information about bacteria

Bacteria are microorganisms, usually unicellular, without a formed cell nucleus. Bacteriology is a branch of microbiology that deals with the study of bacteria. The size of bacteria can vary widely - 0.15 to 50 µm.

In any bacterium there are always three structures:

1. cytoplasmic membrane.
2. Ribosomes are organelles required for protein synthesis
3. A nucleotide that stores the genetic material of a bacterium. It is represented in the form of one chromosome - a DNA molecule.

A cell wall is present on the surface of the cytoplasmic membrane, and on top of it there is often an additional capsule. The capsule and cell wall form the cell wall. Ribosomes and nucleotides of bacteria are located in the cytoplasm. The cytoplasmic membrane together with the cytoplasm is called protoplast.

Some bacteria have flagella that enable them to move through liquid and viscous media. Many on the cell wall have villi, which, according to many researchers, simplify the process of attaching bacteria to the cell.

Reproduction of bacteria

Most bacteria reproduce by binary fission. This is a process in which two identical daughter cells are formed from one parent cell. DNA is replicated in the same process.

Some bacteria are characterized sexual process, as a result of which a daughter cell is formed from two parent cells with non-identical genetic material, with a set of genes from both original cells. The resulting cell (bacterium) is called a recombinant.

What do viruses and bacteria have in common?

1. Both viruses and bacteria can be found anywhere on Earth, in any habitat.
2. Both cause disease in humans, animals and plants. Many of them are deadly.
3. Viruses and bacteria are used in research in microbiology.
4. The genetic material of viruses with double-stranded DNA and bacteria is presented in the same way.

The main differences between viruses and bacteria

1. Dimensions. Viruses are about 1000 times smaller than bacteria.
2. Structure. The structure of viruses differs from the structure of cells of all living organisms, including bacteria.
3. Replication (multiplication). The virus does not replicate outside a living cell, while bacteria can multiply in any environment.
4. genetic material. The genome of a virus can be represented by both DNA and RNA, single-stranded or double-stranded, while a bacterium is characterized by a double-stranded DNA genome.
5. Attachment to the cell. Many bacteria are able to communicate with villi on the surface of the cell wall with cell receptors. In virions, this function is performed by spiny processes on the surface of the supercapsid.
6. Viruses can infect bacteria, just like any other living cells, and use them to reproduce their genetic material. Unlike them, bacteria cannot infect viruses.

All unicellular organisms and some multicellular organisms (fungi) are combined into the concept of microbes, or microorganisms. Pathogenic microorganisms, penetrating into a living being, cause the development of an infectious disease. The body reacts with various symptoms, the nature of which makes it possible to determine the type of infectious agent and the localization of the pathological process. Microbes are divided into several types, among which the main ones are viruses and bacteria.

You can find various microbes in soil, water, air, the body of animals or humans. Microbes receive all the substances necessary for their vital activity through the shell of the host cells, since they do not have digestive organs. Microbes reproduce by budding or division. This process is facilitated by an ambient temperature of about 37-40 ° C.

Viruses are even smaller than other microbes. Therefore, representatives of this species cannot be seen under a conventional microscope - they are available for study only under an electron microscope. Their sizes can be from 8 to 250 nm. Unlike bacteria, they are able to pass through the pores of filters, therefore they are called filterable.

When penetrating into the cells of living organisms, the viral agent forces them to synthesize viral components. The cell is damaged. Such infectious agents can destroy the affected cell or exist in it for a long period of time (in chronic infectious diseases). There are no visible disturbances in such a carrier cell. Antibiotics do not work on these pathogens.

Interesting Facts:

1. Viruses cannot independently produce protein - a genetic set of information.
2. Viruses are the most numerous bioform on planet Earth.
3. About 33% of the components of the human genome are similar to viruses.
4. It is possible to grow this form in the laboratory on cultures from living tissues.
5. Viruses are not able to survive for a long time outside the host body (only a few minutes).

Features of bacterial microorganisms

The difference between microorganisms, first of all, is that bacteria are single-celled microorganisms with many functional abilities. They have a shell and a primitive core.

A certain number of bacteria can cause various infectious diseases. This property is called pathogenicity. Most bacterial organisms can be cultivated on artificially prepared nutrient media. Bacteria multiply by dividing (the whole process takes 20-30 minutes). These microorganisms can be eliminated with antibacterial drugs - antibiotics.

There are bacteria that are not pathogenic. Some of them, on the contrary, help our body - bifidobacteria, lactobacilli. They are essential elements for the normal functioning of human organs and systems.

What are the differences between different microbes?

So, let's sum up. The difference between viruses and bacteria is as follows:

1. Some microorganisms have a cellular structure, while others are non-cellular.
2. Viruses are many times smaller than bacteria and other microbes.
3. The virus enters the cell and destroys it from the inside, and the bacteria from the outside.
4. Bacteria reproduce on their own, while viruses use the cells of a living organism for this.
5. Viral pathogens are unable to maintain their vital activity outside a living organism, and bacteria can form spores (a protective temporary form).
6. Bacterial microorganisms can be both beneficial and pathogenic, and viruses necessarily cause the development of pathology.
7. The difference in the treatment of diseases of viral and bacterial infections.
8. The difference in methods and materials for laboratory cultivation of pathogens of these types.

Who are the representatives of the microcosm - viruses and bacteria - to each other? Can they be considered enemies, friends, blood relatives or partners? We will understand their interaction and role in the human body.

Most often, a person gets acquainted with viruses and bacteria during the cold season. Acute respiratory infections are one of the most common diseases in the world. Most of these diseases occur due to viruses and bacteria that enter the human body along with inhaled air and settle on the mucous membranes of the nose or mouth 1 .

To understand the process of infection, we can draw an analogy with any public institution, which in our case is a human body. Through open doors, various guests enter the institution - viruses and bacteria. Some bacteria are an intelligent public and do no harm, while some are strictly forbidden to enter: they can provoke a real conflict. As for viruses, they are, for the most part, bandits. Don't expect anything good from them.

Against unwanted persons outside and inside the institution there is a security system - human immunity. Sometimes the immune system does not cope with its tasks, gets tired or is “distracted” by bacteria, letting dangerous viruses inside, which immediately begin a raider takeover.

So what is the main difference between them? First you need to clearly understand what they are, and on the basis of this, determine the difference and the principle of impact on the body.

What are viruses

A virus is the smallest organism that can exist and multiply only inside living cells. In the external environment, the virus is found in microparticles of biological material, but it multiplies exclusively in the cells of living beings. In other words, the virus is not active until it is inside a person 2 .

And it gets there like this:

• Airborne, like most respiratory infections
• When drinking dirty water, with food, when hygiene rules are not observed
• From mother to unborn child
• Contact - with close contact through the skin or mucous membranes
• Parenteral way - bypassing the gastrointestinal tract, by injection

After entering the body, the virus first attaches to the cell, then delivers its biological genome into it, loses its shell, and only then multiplies. After reproduction, the virus leaves the cell, and the infectious agent spreads along with the blood, continuing the total infection. Viruses can suppress the immune system 2 .

What is bacteria

A bacterium is a complete, albeit unicellular, organism. She knows how to multiply due to division, which she actively does in nature or inside a person 3.

Not all bacteria cause infectious diseases. Some are useful and live in the organs of the body. For example, lactic or bifidobacteria, which live in the intestines and gastric tract, are actively involved in the process of human life and actually form part of its immune defense 3 .

The entry of bacteria into the body follows the path of viruses. But bacteria multiply more often outside the cell than inside it. The list of diseases that develop as a result of their penetration into the human body is extremely large. Bacteria can cause 3:

• Respiratory diseases (most often they are caused by staphylococci and streptococci)
• Infections of the gastrointestinal tract (provoked by E. coli and enterococci)
• Nervous system disorders (caused by meningococci)
• A number of diseases of the reproductive system, etc.

Reproducing, they spread through the bloodstream, which leads to generalization of the infection and clinical aggravation of the patient's condition. Bacteria are also able to suppress the immune system, making it harder for the body to resist viruses 3 .

How is a virus different from a bacterium

Thus, both viruses and bacteria can infect the body, causing infection. The key difference between them is in the mechanism of reproduction. Viruses cannot reproduce in the external environment, so they need to infiltrate the cell. Bacteria reproduce by division and can live in the external environment for a long time, waiting to enter the human body. Accordingly, the mechanisms for antibacterial and antiviral protection should also differ 4 .

Let's summarize briefly. There are 4 differences between a virus and a bacterium:

• The size and form of existence. A virus is the simplest life form, a bacterium is a single-celled living being.
• Vitality. The virus exists only inside the cell and infects it, after which reproduction (cloning) occurs. The bacterium lives a full life, multiplying by division, and the body for it is only a favorable place of existence.
• manifestation form. Viruses tend to manifest themselves as an increase in body temperature, general weakness, muscle and joint pain. Bacteria manifest themselves as unhealthy secretions (purulent or as a specific plaque).

Typical viral diseases: SARS, influenza, herpes, measles and rubella. They also include encephalitis, hepatitis, smallpox, HIV, etc.

Typical bacterial diseases: syphilis, whooping cough, cholera, tuberculosis, diphtheria, typhoid and intestinal infections, STIs.

It happens that both of them cause the same disease together. Such a symbiosis requires special treatment. Examples are: sinusitis, tonsillitis, meningitis, pneumonia and other diseases 5 .

Fight against viruses and bacteria

It is impossible to completely protect yourself from viruses and bacteria. A person is constantly attacked by a huge number of microorganisms and the main barrier in their path is immunity. Therefore, it is important to strengthen and keep the immune system in a “combat” state, especially during the cold season and during periods of seasonal illness.

The IRS®19 immunomodulator will become an assistant on the way to a healthy and strong immune system. It contains a mixture of bacterial lysates, which are specially isolated parts of pest bacteria. Lysates activate the immune system and direct it to fight bacteria and viruses. The drug has a high level of safety and can be prescribed for the prevention of infections in adults and children older than 3 months. It has been tested many times and has shown excellent results in the fight against infections, including SARS 6 .

According to K. Veze, all living beings are divided into several domains. There are three of them: bacteria, archaea and eukaryotes. Viruses are considered as a non-ranking category. The fact is that not all scientists attribute this group of creatures to the living world. But the majority, like the creator of the RNA world hypothesis, tends to group viruses into a separate domain. And this, despite the fact that bacteria and viruses are the smallest among other creatures, and also quite simply arranged.

The question of the origin of viruses and bacteria remains open. There is not even an exact idea which of these groups appeared earlier. It is logical to assume that viruses and bacteria should have a common ancestor and at least the same origin. The first theories were based on such judgments. But a detailed study of these microorganisms led to the conclusion that the differences between viruses and bacteria are more significant than previously thought.

The difference between viruses and bacteria

The most important of these differences is the way of life that bacteria and viruses have completely different. The first, despite the simplicity of their device, are independent creatures. Even if they live inside a cell. As do, for example, chlamydia. Viruses outside the cell have no biological activity. They do not have any organs for elemental metabolism. A particle of all viruses consists of two elements. This is the genome (it is represented by one or two strands of ribonucleic acid) and a protein shell. Some have an additional capsid on top of the shell.

All viruses, depending on what kind of ribonucleic acid they have, are divided into two large groups: RNA- and DNA-containing.

Viruses can take several forms.

• Icosahedrons.
• Phages.
• Octahedrons.
• Helical.

Bacteria and viruses are quite different in size. If the sizes of the former are measured in units and hundreds of micrometers, then the largest virus is no more than 1300-1400 nanometers. Thus, the largest virus is smaller than the smallest bacterium.

The pathogenicity of viruses depends on the ability to penetrate certain cells.

While the existence of bacteria requires a combination of protection from the aggression of the macroorganism and the ability to rapidly increase in numbers and form colonies. In other words: it is most important for bacteria to "conquer" a certain living space for existence.

Accordingly, both bacteria and viruses have different sensitivity to drugs aimed at their destruction. As antiviral drugs, interferons and their analogues are most effective. To fight bacteria, antibiotics are used, which do not act on viruses.

Entire viruses can be described in several stages. First, the particle enters the cell. The virus genome is then integrated into the cell genome. The latter begins to produce copies of the virus, and the cell organelles switch from their own metabolism to creating shells for these genomes. The virus particles then exit the cell and everything starts all over again.

Viruses pathogenic to humans cause measles, smallpox, rubella, polio, AIDS, colds of the upper respiratory tract, and others. While bacteria are the culprits of whooping cough, diphtheria, typhoid, etc.

It is important to know the difference between bacterial and viral infections. They have a different approach to their treatment. Antibiotics do not act on viruses, so it makes no sense to prescribe them for ARVI, but it is necessary for a bacterial infection.

The human body is prone to a wide variety of diseases, and most of them are infectious. And such diseases can be bacterial or viral in nature. It is important to immediately determine which pathogen caused the disease in order to choose the right treatment. But for this you should know how to distinguish a viral infection from a bacterial one. In fact, there are differences, knowing which, you can quite easily determine the type of pathogen.

Viruses are non-cellular organisms that need to invade a living cell in order to reproduce. There are a huge number of viruses that cause various pathologies, but the most common are those that provoke the development of the so-called colds. Scientists have counted more than 30,000 such microbial agents, among which the most famous is the influenza virus. As for the rest, they all cause SARS.

Even before going to the doctor, it is useful to know how to determine that a child or an adult has SARS. There are many signs indicating the viral origin of inflammation:

• short incubation period, up to 5 days;
• body aches even at subfebrile temperature;
• temperature rise above 38 degrees;
• strong fever;
• severe symptoms of intoxication (headache, weakness, drowsiness);
• cough;
• nasal congestion;
• severe redness of the mucous membranes (in some cases);
• possible loose stools, vomiting;
• sometimes skin rash;
• duration of viral infection up to 10 days.

Of course, all the symptoms listed above are not necessarily manifested in every case, since different groups of viruses cause diseases with different symptoms. Some provoke an increase in temperature up to 40 degrees, intoxication, but without a runny nose and cough, although the redness of the throat is visible upon examination. Others cause severe runny nose, but low-grade fever without severe weakness or headache. In addition, a viral infection can have either an acute or insidious onset. Much depends on the “specialization” of the virus: some species cause a runny nose, others cause inflammation of the walls of the pharynx, and so on. But a characteristic feature of each such disease is that it lasts no more than 10 days, and from about 4-5 days the symptoms begin to decrease.

Signs of a bacterial infection

To have an idea of ​​how to distinguish a viral infection from a bacterial one, it is important to know the features of the pathogenesis of both types of diseases. Bacterial symptoms are:

• incubation period from 2 to 12 days;
• pain is localized only at the site of the lesion;
• subfebrile temperature (until inflammation is highly developed);
• severe redness of the mucous membranes (only with severe inflammation);
• the formation of purulent abscesses;
• purulent discharge;
• plaque in the throat of a white-yellow color;
• intoxication (lethargy, fatigue, headache);
• apathy;
• decreased or complete lack of appetite;
• exacerbation of migraine;
• the disease lasts more than 10-12 days.

In addition to this symptom complex, a characteristic feature of bacterial infections is that they do not go away on their own, and without treatment, the symptoms only get worse.

That is, if ARVI can pass without specific treatment, it is enough to adhere to the correct regimen, take general strengthening agents, vitamins, then bacterial inflammation will progress until antibiotics are taken.

This is the main difference when it comes to colds.

Diagnostics

On the other hand, doctors often face the question of how to distinguish a bacterial infection from a viral one based on more than just symptoms. For this, laboratory tests are carried out, first of all, a general blood test is done. Based on its results, it can be understood whether the disease is caused by a viral or bacterial infection.

A general blood test reflects such indicators as the number of red blood cells, platelets, hemoglobin, and leukocytes. In the study, the leukocyte formula, the erythrocyte sedimentation rate are determined. Depending on these indicators, the type of infection is determined.

For diagnosis, the most important values ​​​​are the total number of leukocytes, the leukocyte formula (the ratio of several types of leukocytes) and the ESR.

Leukocytes are those blood cells that provide protection for the body, their main function is the absorption of foreign particles and pathogens. There are several types of leukocytes:

As for the erythrocyte sedimentation rate, it varies depending on the state of the body. Normal ESR in women is from 2 to 20 mm/h, in men - from 2 to 15 mm/h, in children under 12 years old - from 4 to 17 mm/h.

Blood test for SARS

If the disease is caused by a virus, the results of the study will be as follows:

• the number of leukocytes is normal or slightly below normal;
• increased number of lymphocytes and monocytes;
• decrease in the level of neutrophils;
• ESR is slightly reduced or normal.

Blood test for bacterial infection

In cases where various pathogenic bacilli and cocci became the cause of the disease, the study reveals the following clinical picture:

Not everyone may understand what metamyelocytes and myelocytes are. These are also blood elements that are normally not detected during analysis, since they are contained in the bone marrow. But if there are problems with hematopoiesis, such cells can be detected. Their appearance indicates a severe inflammatory process.

Importance of Differential Diagnosis

It is important to know how a bacterial and viral infection differs, since the whole point is in a different approach to their treatment.

Everyone knows that antibiotic therapy has no effect on viruses, so there is no point in prescribing antibiotics for ARVI.

Rather, they will only harm - after all, such drugs destroy not only pathogenic, but also beneficial microorganisms, which partially form immunity. But with a bacterial infection, the appointment of antibiotics is mandatory, otherwise the body will not cope with the disease, and it will at least become chronic.

This is what diseases are all about. However, despite the differences, the same therapy is sometimes prescribed for bacterial and viral infections. As a rule, this approach is practiced in pediatrics: even with an obvious viral infection, antibiotics are prescribed. The reason is simple: children's immunity is still weak, and in almost all cases a bacterial infection joins the virus, so the prescription of antibiotics is fully justified.