1. The nature of viruses.
2. The origin of viruses.
3. Place of viruses in the biosphere.
4. Selected forms of viruses (bacteriophages, prions, eyelids, plants viruses, viruses of mushrooms and algae).
Later, when studying moderate bacteriophages, data were obtained contrary to the definition of viruses as organisms, as they are, according to A. Lvov, "independent units of interrelated structures and functions". The basis of this judgment was the fact that the genome of individual bacteriophages integrates into the bacterial genome as it occurs in oncogenic viruses with the formation of a separate form of existence of viruses - provirus. At the same time, the expression of their genome may be different. With complete expression, the formation of mature virions occurs, only some proteins are formed with incomplete.
The concept of the presentation of viruses as the body collapsing, if we consider such structures as viroids, viruses and plasmids.
Satellite viruses are widespread in nature. They are not able to reproduce without complete viruses, in particular adenoviruses.
Plasmids are Circular DNA sections. They are not able to replicate, and they replicate enzyme bacteria systems.
Viroids - RNA structures with a small molecular weight, on which even one polypeptide cannot be encoded, so they cannot be attributed to viruses.
Thus, nature and origin of viruses remain the most complex issues of virology, distant from permission. Until now, relative to the nature of viruses there are two diametrically opposite judgments.
There are several hypotheses of the origin of viruses.
1st Hypothesis (1935).
2nd hypothesis.
3rd hypothesis (1964)
According to this hypothesis, nucleic acids occurred in nature abiogenic, regardless of the living system.
4th Hypothesis (1967).
According to this hypothesis, viruses are separable cell components containing nucleic acids and endowed with autonomous scheduling elements. This hypothesis has the largest number of supporters. Some DNA viruses could arise from the epis and mitochondria. For example, the hepatitis virus is similar to cell mitochondria, and the vapors are structures similar to T-RNA.
Ecology is the science of the organization's relationship with the environment.
The transformation of the biosphere is a powerful factor affecting the evolution of viral infections. All this leads to a change in biocenoses, which entails the change in the immune system of the macroorganism.
The transformation of the biosphere occurs for many reasons, among which the mainstream is the use of antibiotics, pesticides, vaccines and other agents directly affecting the biosphere and its components.
The main properties of viruses that distinguish them from bacteria:
1. Very low value (measured in nm).
2. Lack of cellular structure.
3. The presence of only one nucleic acid.
4. Lack of autonomous metabolism and energy connection of the virus with a host cell.
5. Presence of tropism.
6. Disconnected type of reproduction.
7. The ability to cause intracellular inclusions.
9. The stability of viruses to low temperatures, antibiotics and sulfonamides.
10. The presence of pluralism in many viruses.
Bacteriophages.
Bacteriophages have a characteristic inherent morphology. All bacteriophages contain a head that is built of capsages located in the form of a polygon. Inside the head caps contains nucleic acid of bacteriophage. Most bacteriophages also have a process (tail) attached by one end to the head. In the complex phages, the process consists of a hollow rod formed by spiral laying of structural proteins. In addition, the structure of the process may include a phage plate and protein thread-receptors located at the free end of the process. The process is designed to attach to the receptors of a bacterial cell and providing penetration of the phage nucleic acid penetration.
The size of the head of most phages is 20-90 nm, and the process is from 100 to 200 nm with a thickness of 2.5-3 nm.
Due to the variety of morphological features of bacteriophages, there are five major morphological groups: (1) bacteriophages with a declining process, (2) bacteriophages with a long non-developing process, (3) bacteriophages with a short process, (4) bacteriophages without a process. (5) Fit-shaped phages. The first three morphological types contain a bunk DNA, the fourth - one-grant RNA or DNA, fifth - one-dimensional RNA.
Depending on the type of infection, bacteriophages are divided into virulent and moderate. Viruble bacteriophages give a lithic productive infection, that is, the cell infection leading to the lysis of the bacterial cell and the release of the new generation of bacteriophages.
Moderate phages cause an abortive lease infection, in contrast to virulent bacterophages, that is, an infection that does not lead to the formation of a new generation of bacteriophages. In most cases, this is due to the integration of the genome of the bacteriophage in the cell genome and the transition of the virus into the state of the provinus. This state of the bacterial cell is called lyzogenia. In this case, the productive infection is observed only at a limited amount of bacterial population. However, the impact of certain physical factors (UV radiation) can increase the percentage of bacterial cells with a productive infection due to the activation of the provirus.
Viroids.
More than 16 diseases of plants are caused by a special group of infectious agents called by viroids. They are ring single-grade RNA molecules containing from 250 to 370 nucleotides. The virutes are transmitted from the plant to the plant mechanically or with pollen. After infection, the eyelids are found mainly inside the nucleus of the affected cell in an amount of from 200 from 10,000 copies of nucleic acid. It is known that viroid nucleic acid molecules do not function as a RNA and do not regulate protein synthesis. There remains an unexplained mechanism for the appearance of symptoms in affected plants. Sometimes the virutes cause latent plant infections.
Although the viroid RNA can be replicated by RNA-dependent RNA polymerase, the replication of the VIRID RNA comes with the participation of a cell enzyme that perceives RNA as a cell DNA thread.
The most studied are viroids that cause potato diseases. They contain an annular RNA containing 359 nucleotides and packed as a short chopstick by combining complementary nucleotide pairs inside the nucleic acid. Several strains distinguished by virulence are isolated. As it was found, this is due to a change in the nucleotide sequence in two short areas of the Viroid RNA.
Prions.
Among the infectious agents, causing diseases of people and animals allocate a special group called by Prions. They obtained this name due to the fact that they include only protein, as a result of which they are also called protein infectious agent (PRP). Until now, not a single nucleotide was found in the composition of the prions, but only the presence of protein with a molecular weight from 33 to 35 D. It also found that the gene encoding this protein is present in many vertebrates and even invertebrates. Therefore, the possibility of animal origin of prions is not excluded.
Until now, the mechanism for the development of prion diseases has not yet been established. It is believed that the infection causes a changed protein of the organism, which, in the presence of the necessary chemical factors, is able to cause destruction and death of cells. However, this hypothesis is not consistent with the data on the existence of several strains of one and tog of the same prion. Another hypothesis states about the composition of prions include a short nucleic acid section enclosed in PrP protein.
Prions cause so-called slow infections in humans and animals - granio-shaped encephalopathy, Kuru, Creitzfeld-Jacob's disease and others.
Plant viruses.
Plant viruses are not so well studied as animal viruses. This is caused by the difficulties of their cultivation, since for them it is necessary to obtain a special type of sensitive cells derived from plants. However, the fact is established by the fact of transferring the majority of plant viruses through insects, so it has now become possible to cultivate plant viruses in cell cultures obtained from cells of various insects.
Morphology of plants viruses is not much different from the morphology of animal viruses. Most contain a rigid or flexible spiral capside, separate viruses have a cubic cap, as well as a capsid of a cubic type of symmetry with the presence of additional capsages on the surface. Almost all plant viruses are RNA-genome viruses containing one or a two-grated RNA molecule. Exceptions are only Caulimovirus and Geminivirus containing DNA.
Reproduction of plants viruses is not much different from animal viruses. The main difference is that an enzyme is present inside the plant cell to replicate RNA, so in the process of reproduction, most plant viruses use a cell enzyme. The virion assembly is also somewhat different. At the final stage of RNA replication, it is associated with capsumbers on the 3 'end of the genome, subsequently the addition of nucleic acid helix cohesives, like hollow discs on the rod with the formation of a mature virion.
Methods for transmitting plant viruses are different - with wind, insects, nematodes of plants, mushrooms, etc.
Viruses of mushrooms and algae.
Most viruses are isolated from Aspergillus and Penicilium generic mushrooms and contain a double-grant RNA molecule enclosed in a cubic capside. All viruses of mushrooms and algae have the size of about 25-50 nm.
It has long been a dispute about what viruses are living or non-living. Indeed, viruses are very simply arranged, do not have a cell organization, can crystallize. Another D.I.Ivanovsky found in the cells of tobacco leaves affected by mosaic disease, crystalline formations. They are called "Ivanovsky crystals." Crystallizability does not fit into our ideas about live. Viruses do not have independent metabolism, at the stage of synthesis of the components of the virion, it exists in the "disassembled" form, its separate components These are molecules of nucleic acid and protein viruses can exhibit their infectious properties even if there are only in the form of a single nucleic acid molecule - the infectiousness of the virus nucleic acid. All this speaks of viruses as non-living agents.
However, on the other hand, viruses have the ability to maintain their individuality, separation from the external environment, ensure, although peculiar, reproduction of their genotype and phenotype. For viruses, the phenomena of heredity and variability are characterized, they evolve under the laws common to all living things. This confirms the living nature of viruses.
Apparently, the solution of the issue of virus nature has more general theoretical, than practical importance and is associated with the problem of determining the living. With the opening of viruses, our ideas about the essence of life were expanded and deepened.
But we, doctors, should come to this issue with pragmatic positions. Viruses are causative agents of viral infectious diseases. And the infectious process, in contrast to intoxication, is the process of interaction between two living beings. Viral diseases arise and apply to the laws of infectiology, they require the use of the same methods of prevention and treatment as infections caused by other microorganisms. Therefore, from the point of view of practical medicine, we will consider viruses as living pathogens of infectious viral diseases requiring the use of medical and preventive and anti-epidemic measures.
The question of the origin of viruses, as can be understood, does not at present a reasonable solution. It is closely related to solving the problem of the origin of life on Earth. But one should consider the main hypotheses about the origin of viruses.
The second hypothesis can be designated as a hypothesis of "Protobyott". It suggests that viruses are descendants of the simplest living beings that were the priests of all living things and formed from non-living organic material. In the future, there was an evolution of these formations towards the formation of cell organisms, and viruses are relicy descendants of such protobilists. This hypothesis developed intensively by Soviet virologists. However, it is very difficult to explain how such primary viruses could also be reproduced in the absence of cells. After all, viruses are not able to multiply without the use of orger cells and enzyme systems of cells. Therefore, at present, the hypothesis about the origin of viruses from the primary oriental forms of life is not divided by most virologists.
The third hypothesis can be defined as the hypothesis of "bent genes". It suggests that viruses are genetic cell elements that have made and acquired the ability to autonomous existence. The hypothesis explains well and the diversity of genetic material of viruses, and the possibility of their existence and evolution.
It is necessary to recall that bacteria has similar genetic structures that can be transmitted from some bacterial cells to others and is reproduced in them. This is plasmids. Plasmids are small DNA ring molecules with certain autonomy. They can be reproduced in bacterial cells or integrate into bacterial chromosome. These properties of plasmids are similar to the properties of viruses. By the way, FAG, the virus of bacteria, we belong to plasmids in the form of proofag.
It can be imagined that viruses are areas of nucleic acids surrounded by protein shells. The virus shell provide him with the opportunity to persist in extracellular state and penetrate the cell. It is this hypothesis that is divided into many virologists now. You can express hope that with the development of our knowledge about living we solve and the problem of origin of viruses.
1. Pyatk ³n K. D., Krivoshes Yu.S. M³Krobdl³ology. - K: Higher School, 1992. - 432 p.
Timakov V.D., Levashev V.S., Borisov L.B. Microbiology. - M: Medicine, 1983. - 312 p.
2. Borisov L.B., Kozmin-Sokolov B.N., Freidlin I.S. Guide to laboratory classes on medical microbiology, virology and immunology / ed. Borisova L.B. - G.: Medicine, 1993. - 232 p.
3. Medical Microbiology, Virology and Immunology: Textbook Ed. A.A. Vorobyva. - M.: Medical Information Agency, 2004. - 691 p.
4. Medical microbiology, virology, immunology / ed. LB Borisov, A.M.Smirnova. - M: Medicine, 1994. - 528 c.
5. Bukrinskaya A.G. Virology. - M.: Medicine, 1986. - 336 p.
Lecture 22. Features of infection and immunity in viral diseases
Ministry of Common and Vocational Education
Sverdlovsk region
GOU SPO "Krasnoufim Pedagogical College"
Viruses and Naturetheir origin
Executor:
Dmitrieva I.Yu.,
student 23 groups
Leader:
Kaptsieva O.V.,
teacher
natural scientific
disciplines
krasnoufimsk
Passport
Project name: "Viruses and nature of their origin."
Project Manager: Kaptiyev O.V.
Academic subject, within the framework of the project
Natural science.
Educational discipline is close on the subject of the subject of biology.
Project Type: Creative.
The age of students for which the project is 16-18 years old.
Necessary equipment: educational literature, photos,
computer, printer, scanner.
Introduction
Nature of origin viruses
What are the non-calm forms of life?
How does the virus penetrate the cage?
The method of breeding viruses
What is AIDS?
Harm and benefit of viruses
America first approved viruses as a food additive
Conclusion
Bibliography
Introduction
A variety of life on Earth is difficult to describe. It is believed that now in our planet in excess of millions of animal species, 0.5 million plant species, up to 10 million microorganisms, and these figures are underestimated. No, never will never have a person who would know all these species. Moreover, an acute need occurs in the system of wildlife, guided by which we could find a place for the body that is interested in it, whether it is a bacterium that causes a new disease, a new beetle or tick, a bird or fish. People realized this need back in the questioned century.
It was then that the Great Swedish Naturalist Karl Linney created a scientific system of wildlife, which we use and at present. An account of the age of scientific systematics is conducted from 1758, when the 10th edition of the Linneyevskaya "Nature System" was published. The basic principles of Linneia and the names of the species, data to them, are still preserved, although the species are now known thousand times more.
In our world there are a large group of living beings that have no cellular structure. These creatures are the names of viruses (lat. "Virus" - poison) and no non-calm forms of life. Viruses can not be attributed to any animals or plants. They are extremely small, therefore can only be studied using an electron microscope.
Viruses are able to live and develop in cells of other organisms. Setting inside the cells of animals and plants, viruses cause many dangerous diseases, such as tobacco mosaic disease, pea and other cultures (in plants). In the study of prokaryotic and viruses, the Linneevskaya system is fully applied. In his times, almost anything knew about the world of microorganisms.
Therefore, the forms of viruses and bacteria in the system are often indicated by non-sonorous Latin letters, but combinations of letters and numbers. Viruses have genetic connections with representatives of the Flora and the fauna of the Earth. According to the latest research, the human genome is more than 30% of the information encoded by virus-like elements and transposons. With the help of viruses, the so-called horizontal transfer of genes (xenology) can occur, that is, the transmission of genes between two unrelated (or even relating to different types) features.
We chose this topic, as we believe that it is very relevant in our time. Many scientists are struggling with dangerous, deadly viruses since the time they were discovered.
From my point of view, the fight against viruses will always be until scientists find a means that will destroy these organisms hazardous to human life having a non-gland structure.
It is very difficult to deal with these organisms, since they have a property to change the composition of their structure when entering favorable conditions.
When writing the project, we set themselves the following goal: to study the essence of the origin of viruses, their structure and role in nature.
1) Pick the necessary information sources;
2) to work this information and relate it to the problem under study;
3) consider the discovery of scientists in order to study the structure of viruses;
4) find positive and negative qualities of viruses;
5) prepare for the protection of the project.
Nature and origin of viruses
Modern ideas about viruses were gradually developed. In 1892 DI. Ivanovsky drew attention to the widespread tobacco disease, in which the leaves are covered by paint stains (mosaic disease). After the discovery of viruses, Ivanovsky was considered simply very small microorganisms that are not able to grow on artificial nutritional media. Shortly after the discovery of the tobacco mosaic virus, the viral nature of FMD was proved, and after a few years, bacteriophages were opened. Thus, three main groups of viruses, affecting plants, animals and bacteria, were opened. However, for a long time, these independent sections of virology developed in isolated, and the most complex viruses - bacteriophages - for a long time were considered not living matter, but something like enzymes. Nevertheless, by the end of the 20s - the beginning of the 30s it became clear that viruses are living matter, and approximately the names of the filtering viruses, or ultraviruses, were entrusted.
In the late 1930s - early 40s, the study of viruses was progressing so much that doubts were disappeared in living nature, and a provision for viruses as organisms were formulated. The basis for recognizing viruses by organisms was the facts obtained in their study, testifying that viruses, like other organisms (animals, plants, simplest, mushrooms, bacteria), are able to multiply, possess heredity and variability, adaptability to the changing environment of their habitat and, Finally, the exposure of biological evolution provided by natural or artificial selection. This is, above all, the interaction of two genomes - viral and cellular.
According to the third, viruses are derivatives of cell genetic structures that have become relatively autonomous, but preserved the dependence on cells. The third hypothesis of 20--30 years seemed unlikely and even received the ironic name of the hypothesis of begging genes. However, the accumulated facts give all new and new arguments in favor of this hypothesis. Along with this, a significant number of facts have accumulated on the existence of the existence in nature on a wide scale of the exchange of ready-made blocks of genetic information, including representatives of different, evolutionary distant viruses. As a result of such a exchange, hereditary properties can quickly and jump, by embedding alien genes (borrowing the gene function). New genetic qualities may also arise due to an unexpected combination of own and integrated genes (the occurrence of a new function). Finally, a simple increase in genome due to non-working genes opens up the possibility of the evolution of the latter (the formation of new genes).
What are the non-calm forms of life?
Bites hurt and hurt,
Although it is sometimes not visible ...
J. Swift.
"Well, let our wonderful stranger remain a stranger, if only she loved us,"? Said, according to legend, an outstanding microbiologist L. Paster, and I can't manage to highlight the causative agent of rabies? A terrible disease, from which there was no salvation in the XIX century. Get the vaccine and thereby knowing the nature of the infectious agent and save many thousands of human lives he managed. Nobody could do this in those days, since the causative agent was not a microbe, as expected L.Paster, but a virus.
Along with unicellular and multicellular organisms in nature there are other forms of life. These are viruses that do not have a cellular structure. They represent the transitional shape between living and inanimate matter. Viruses arranged very simple. Each viral particle consists of RNA or DNA enclosed in a protein shell, which is called capsid Fully formed infectious particle called virion. In some viruses (herpes or influenza) there is also an additional shell, which arises from the plasma membrane of the host cell. Viruses are able to live and multiply only in cells of other organisms. In the external environment, they do not show any signs of life, many have the form of crystals. The magnitude of viruses ranges from 20 to 300 nm.
The virus has a rather complicated internal structure. Its core (core) contains one (sometimes more) nucleic acid molecule (DNA or RNA). Nucleic acids of the smallest viruses contain 3-4 genes, and the largest viruses have up to 100 genes. Outside the virus is covered with a protein "case", protecting nucleic acid from harmful environmental impacts. The form of viruses is very diverse. In size, viruses are divided into large (300-400 nm in diameter), medium (80-125 nm) and small (20-30 nm). Large viruses can be seen in an ordinary microscope, smaller studied under an electron microscope.
How does the virus penetrate the cage?
Plant viruses, whose cells besides the membrane are protected by a durable fiber shell, can only penetrate them in places mechanical damage. The pedigrees of these viruses can be arthropod - insects like floss and ticks with a sucking apparatus. They transfer virions on their trumps. And a person can be mosquitoes (yellow fever), mosquitoes (Japanese encephalitis) or mites (taiga encephalitis). Previously, all viruses extending with the help of bloodsuckers were combined into a group arbovirusov.
Unsolvented animal cells protected by one membrane are more vulnerable to viruses primarily due to their ability to phage - I. pinotozetozoa. Capturing nutrients, they often "swallow" and virions. If the cells are connected to each other, like the cells of the nervous system, the virus can travel along these contacts, infecting one cell per different. This is usually a slow process (this is how infection occurs, for example, when the bite of a mad animal).
Finally, many viruses develop special devices for penetration into the cell. Cells lining the respiratory tract are covered with a protective mucus layer. But the flu virus dilutes the mucus and penetrates the membrane (because the first symptom of influenza is often a runny nose).
AIDS virus infects white blood bodies of our blood - leukocytesUsing proteins that stick out from the surface of its shell, "stolen" from the master's cell.
In this picture you can see how viruses penetrate the cage. On the left and in the center of the bacteriophage of the intestinal stick: when cutting the tail, the DNA thread from the head is injected into the cytoplasm of the bacterial cell. Right - human cell infection by the AIDS virus. Glycoprotein GP 120 shell sticks with a specific CD 4 protein; GP 41 skeys the membrane of the master's cell, as a result, the RNA protein capsule passes into the cytoplasm, and the empty shell of the virion is discarded.
Classification of organisms based on cell theory. The overall characteristics of viruses and their biological and environmental role on Earth.
When studying the organic world of the Earth, it was found that organisms for their structure can be divided into two large groups: cellic and noncholek Forms. Most organisms have cellic Building, and only organisms forming the kingdom Viruses, have noncellingstructure.
Viruses were opened by D.I. Ivanovo in 1892, and in 1917. Felix Dael opened the bacteriophage - a virus affecting bacteria. Viruses form the kingdom Precele or Viruses. These are organisms having very small sizes (from 20 to 200 nm (nanometers)). Viruses are not capable of growing and their livelihoods can only be carried out inside the host cell.
The biological and environmental role of viruses is that they are a factor in evolution, causing the death of weakened individuals and contributing to the survival of organisms more adapted to this environment.
The method of breeding viruses
Virus (from lat. virus-poison) - microscopic particle capable of infecting cells of living organisms.
Virology (from Virus and Logos - Word, Teaching), Science of viruses. General virology is studying the nature of viruses, their structure, reproduction, biochemistry, genetics.
The method of breeding viruses is also different from division, kinding, disputes or sexual process, which occur in single-cell organisms, in cells of multicellular organisms and in the latter as a whole. Reproduction, or replication, as usually denote virus reproduction. The formation of virions occurs either by the assembly itself (packing of viral nucleic acid into protein capsides and the formation of nucleocapsid), or with the participation of the cell, or both methods (shell viruses). Of course, the opposition of mitotic division of cells and replication is not absolutely, since methods of replication of genetic material in DNA-containing viruses do not differ in principle, and if we consider that the synthesis of genetic material in RNA-containing viruses is also carried out according to the matrix type, then the relative is opposed Mitosis and replication of all viruses. And, nevertheless, the differences in the methods of breeding cells and viruses are so significant that it has to share the entire living world for viruses and universities.
What is AIDS?
There are many viruses in the world that cause dangerous diseases of the disease, such as rabies, encephalitis, polyemete, immunodeficiency, flu, including ...
Medical, veterinary and agricultural virology explore pathogenic viruses, their infectious properties, develops measures for preventing, diagnosing and treating diseases caused by them.
Nowadays, a serious problem is AIDS (acquired immunodeficiency syndrome). This is an epidemic disease of a person affecting a predominantly immune system, which protects the body from various pathogenic agents. Infection of the human cell immunity system is manifested by the development of progressive infectious diseases and malignant neoplasms, and the body becomes defenseless to microbes, which in normal conditions do not cause diseases.
For the first time, AIDS was officially registered in the United States in 1981, and in 1983. It was possible to prove that it was caused by an unknown manic virus, from the Retrovirus family. The composition of this
the virus enters only his inherent enzyme - reversal. Its discovery was a real revolution in biology, as it was shown the possibility of transmitting genetic information not only by the classical DNA scheme\u003e RNA\u003e protein, but also by reverse transcription from RNA\u003e DNA.
The causative agent of the disease is a human immunodeficiency virus (HIV). The HIV genome is represented by two identical RNA molecules consisting of about 10 thousand pairs of grounds. At the same time, HIV, isolated from various AIDS patients, differ from each other by the amount of bases (from 80 to 1000). HIV has a unique variability, which is 5 times higher than the variability of the influenza virus and 100 times greater than that of the hepatitis V virus. The continuous genetic and antigenic variability of the virus in the human population leads to the emergence of new Virion HIV, which sharply complicates the problem of obtaining a vaccine and makes it difficult Special prevention of AIDS. Moreover, this property of HIV, according to a number of specialists, is questioned by the possibility of creating an effective vaccine to protect against AIDS.
One of the manifestations of human infection with the AIDS virus is the defeat of the central nervous system. For AIDS, a very long incubation period is characteristic (calculated from the moment of infection until the first signs of the disease). In adults, it averages 5 years. It is assumed that HIV can persist in the body for life. This means that until the end of your life, infected people can infect others, and under appropriate conditions can be infected with AIDS.
One of the main ways to transmit HIV and the spread of AIDS - sex, since the pathogen is most often in the blood, sperm and vaginal discharge of infected people.
AIDS security guarantee is a healthy lifestyle, the fortress of marriage and families, a negative attitude towards sexual perversions and promotion, random sexual relations.
The following is a schematic representation of viruses: O - shell of the osse virus; B - protein inclusions. Left - Virion Scheme AIDS virus; P - specific proteins of the virus; GP - virus glycoproteins; 1 - membrane, "stolen" at the host cell; 2 - RNA molecules in a protein shell; 3 - protein molecules transforming RNA in DNA.
Harm and benefit of viruses
Many viruses are the cause of dangerous human diseases. In addition to AIDS I. oncogenicCancer Cancer, These include pieces of osse, measles, rabies, poliomyelitis, influenza, sharp respiratory diseases: Orz, yellow fever, herpes (they say: "fever poured on the lips") and even viruses causing warts.
However, not all diseases caused by viruses have learned to successfully prevent and treat. We have not learned to treat and immunodeficiency, and, as a rule, this is a terrible disease in a few years leading to death. And a completely unresolved problem - cancer. Learn successfully, fighting viruses causing malignant tumors to doctors of the future.
What good can be from viruses? After all, these are the enemies of all living things. The benefit may be if the virus is the enemy of the enemy, which means that it is not in all cases the action of the virus is negative. If he attacks one-cell organisms to which, in particular, belong bacteria, they die. Therefore, with the help of such viruses, bacteriophages, the bacteria can be destroyed, causing such hazardous diseases as dysentery, cholera, plague.
The ability of the virus to kill the cell - the owner can be used when combating individual cells of multicellular organisms, and above all - cancer. At the same time, the key to success is the exact "pressing" of the virus to the cell, which is to be killed, because he is in itself ready to hit all the cells sensitive to it. For this, the virus, and special protein, the antibody capable of selectively binding to the cell surface area - targets, are attached to the nanoparticle acting as a kind of vehicle. Such a "shell" attacks only certain cells destroying them. Of course, you need to take care and that the virus can leave the body without damaging healthy cells. In nanotechnology, viruses also use as a "template" to create nanostructured systems.
Some viruses causing insect diseases are used to combat the pests of rural and forestry. However, it should be recognized that the harm, brought by these simple forms of life. Many times bigger their favor.
America first approved viruses as a food additive
An unusual method of combating dangerous infectious diseases, such as licheniosis, offered American scientists. Viruses - bacteriophages, safe for humans, will be sprayed on meat products, ready to use to kill mortal bacteria. The method approved by American Food Control Office and Medications.
Liseriosis, including through infected food, thousands of people are sick annually, and approximately 500 of them die. The yield found a biotechnology company. She came up with a "cocktail" from six viruses, deadly for bacteria Listeria Monocytogenes. Viruses are proposed to spray in mass order on meat products ready for use: chopped ham, hot dogs, sausages, sausages, as well as various products from poultry.
This specially prepared and purified cocktail passed all the necessary tests - no side effects and no visible change in treated food did not occur.
Conclusion
In the course of the project, I still made sure that the acute struggle with viruses life-threatening person is needed. And this is also very laborious work, as the viruses can mutate, i.e. change in its composition. That is why it is very difficult to find a medicine, for example, against immunodeficiency virus.
Nowadays, viruses are studied by scientists from all over the world. Humanity is trying to benefit from them. We have already learned how to get rid of bacteria causing various diseases with bacteriophages.
Maybe in the future, the fight against viruses will not be such a serious problem as now.
There is not a single organism in nature, which would only bring harm and destroyed other organisms. After all, for something he was created by nature?
I think that I fully revealed the topic of my abstract and solved all the tasks set in front of you, which worked as much as possible all the literature on this topic.
I also believe that this topic is very relevant, it is really needed when studying natural science. After all, we get new knowledge about viruses, we are aware of all the danger that they can cause every living organism on our planet.
Bibliography
1. Bogdanova T. L. Biology: tasks and exercises. Manual for applicants to universities. - M.: Higher School, 1991.
2. Knorre D. G., Miazina S. D. Biological Chemistry: Textbook for Chem., Biool. and honey. specialist. universities. - M.: Higher School, 2000.
3. Lemeza N. A., Kamluk L. V. Biology in matters and answers: Tutorial / Hood. oblast M. V. Dranko. - MN: LLC "Popurri", 1997.
4. Mednov B. M. Biology: forms and levels of life. - M.: Enlightenment, 1994.
5. Polyansky Yu. I. General biology: studies. For 10-11 cl. environments shk. - M.: Enlightenment, 1993.
6. Tupikin E. I. General Biology with the basics of ecology and environmental activities: a training manual for the beginning. prof. Education. - M.: Educational and Publishing Center "Academy", 2002.
Nature viruses
The existence of viruses was first established in the study of tobacco mosaic disease. It turned out that the causative agent of this disease can pass through a porcelain filter, commonly used for trapping bacteria. Virus size ranges from 17 to 300 nm in diameter. Thus, in magnitude, they are comparable to molecules, for example, a hydrogen atom has a diameter of about 0.1 nm, and the size of the protein molecule on average is equal to dozens of nanometers.
Viruses are multiplying only in living cells. Many of them are highly specific in relation to the type of infected cells. They radically change the biosynthetic processes of the host cell. In this case, the nucleic acid of the virus switches the cell to the synthesis of virus specific structures, thus competing with its genetic apparatus. For example, respiratory viruses multiply in the cells of the respiratory mucosa, causing characteristic cold symptoms. Most often, viruses have a narrow circle of owners. One of the rapid methods for identifying unknown bacteria can be the use of specific bacteriophages that destroy certain bacterial cells. Conversely, the reaction of some plant species to an unknown virus can be used (in conjunction with other methods) to identify this virus.
Until the 1930s. Viruses were considered as the smallest bacteria. In 1933, this point of view was refuted. Waydel Stanley, who worked in the Rockefeller Institute, received a tobacco mosaic virus extract from infected plants and cleaned it. The purified virus was deposited as crystals. Crystallization is one of the main tests for the presence of a chemically pure compound that does not contain impurities. Thus, it became clear that from a chemical point of view, the virus is much easier than a living organism. When Stanley dissolved the needle crystals and struck the tobacco leaf, then the characteristic symptoms of the mosaic disease appeared again. Thus, it was shown that the virus retains infectiousness after crystallization and resuspensation.
Most of the viruses of plants, like a tobacco mosaic virus, contain only RNA, while other viruses are only DNA. In contrast to viruses, all cells contain both types of nucleic acids. Viruses are deprived of ribosomes, as well as enzymes needed for protein synthesis and energy generation. In this regard, viruses are fundamentally different from organisms having a cellular organization.
Viroids and other infectious particles
There are several molecular pathogens like viruses and. Apparently the bacteria and eukaryotes occurred from the genome. There are also special importance among them by vills, which, despite their name, differ sharply from viruses.
Viroids are the smallest of the famous causative agents of diseases. They are much less than the smallest viral genomes and are deprived of a protein shell. Also known only by plants. They consist of a single-satellite RNA molecule, which is autonomically replicated in infected cells. The virutes were identified as causative agents of dangerous diseases. One of them caused the death of millions of coconut palm trees in the Philippines over the past fifty years, another caused damage to industrial breeding chrysanthemums in the United States in the early 1950s.
The first viroid - the beliefs of potato tubers, or PSTV - was identified by Theodore Dinor from the US Agricultural Department in 1971. Potato tubers infected with PSTV have an extended and curved shape. Sometimes deep cracks appear on them. PSTV is the largest Virion from the above known. Its RNA consists of 359 bases and has either the form of a closed ring, or the structure of the type of heel. In both cases, complementary pairs of bases are connected by hydrogen bonds, forming a two-way RNA, similar to DNA. Under the electron microscope, both form PSTV looks with ropes; The length of them is 50 nm. Although this is the largest virion, its size is only one tenth of the genome of the smallest virus. Viroids are found only in the nuclei of infected cells. They are replicated like viruses, i.e. synthesizing the complementary chain that functions as a matrix. At the same time, the viroids use enzyme host cell systems.
Since the viroids are localized in the core and, probably cannot work as mRNA, it is assumed that they cause diseases, interfering with the processes of regulation of the host cell genes. Some proteins in plants infected cells are present in large quantities than in healthy. Although nucleotide sequences, complementary PSTV are not found in healthy plants, it is assumed that PSTV could occur as a result of changing the genome of some types of potatoes - its main owner.
In living organisms there are molecular pathogenins that are not related to viroids. The existence of structures similar to the viroids, but fired from DNA, is also assumed in animals. They are called "sub-visor particles." It is surprising that some fragments of proteins are able to control their reproduction in animal cells without the participation of nucleic acids, such particles are called "prions".
The beginning of the history of virology is associated with the name D.I. Ivanovsky, who in 1892 published work on the study of tobacco mosaic disease. He noted that the causative agent is the smallest being, passes through bacterial filters, does not grow on nutritional media, invisible in the light microscope.
In 1898, Lefefler and Fossu opened the e-mail virus.
In 1901, Reed and Carrolol allocated a virus from the corpses of people who died from the yellow fever.
Dўerrel in 1910 discovered viruses of bacteria - bacteriophages.
Viruses are widespread in nature, the environment and practically omnipresents. They are in air, water, food, space and in living organisms, and viruses bacteria - bacteriophages - in bacteria.
Medical virology studies only viruses, pathogenic for humans or significant for medicine (bacteriophages).
The main task of medical virology is the study of morphology, physiology, genetics, ecology and evolution of viruses and the development of methods for diagnosing, treating and preventing human infections.
The main properties of viruses:
Consist of proteins and one nucleic acid (DNA or RNA), where all genetic information of the virus is encoded,
Do not have their own metabolic and energy systems,
Using ribosomes host cells for the synthesis of own proteins,
Have a special way of reproduction - diauncutive (disassembled) reproduction: nucleic acids and virus proteins are separately synthesized separately, and then they are assembled into viral particles.
Can integrate their gene in the cell genome with the formation of the provirus,
Viruses have small sizes (from 15 to 250 nm or more).
Like other forms of life, viruses have heredity and variability, preserve viability in freezing, drying, resistant to antibiotics, but are sensitive to high temperature.
Virus Outside Cell - virionHas nucleic acid (DNA or RNA) and a protein shell, is able to crystallize, has infectiousness, i.e. Due to address proteins, attachment proteins, enzymes penetrate into the cell, where it is called " virus", integrated with DNA host virus called provirus.
In addition to typical viruses, unusual infectious particles are known - prions and viroids.
Prions – protein Infectious particles that have a form of fibrils with a size of 10-20x100-200 nm, a mass of 30 kD, do not contain nucleic acid, resistant to heating, to the action of proteases, ultraviolet rays, ultrasound and ionizing radiation. Prions arise as products of mutation of their own gene or fall into the body when eating meat of animals containing prions. Prions accumulate in the affected organ without causing cytopathogenic action (CPD), immune response and inflammatory reactions. They can block or activate human or animal genes.
Viroids - These are small molecules of ring superpiralized RNA, not containing protein causing diseases in plants, perhaps in mammals.
Classification of viruses
By virtue of their characteristics, viruses are highlighted in a separate talent Virain which the type of nucleic acid is distinguished ribovirus and deoxyribovirus (Table 1).
The facilities are divided into families that are divided into subfaming and childbirth. View - A set of viruses with almost identical genome (DNA or RNA), properties and ability to cause a certain pathological process. The names of the family have the end viridae.Submissions - virinae., kind - virus..
Signs used to classify viruses: 1) type of nucleic acid - DNA or RNA; 2) their structure (single-type, bieting, linear, ring, fragmented, nephrimbted with repeating and inverted sequences); 3) structure, dimensions, type of symmetry, number of capsages; 4) the presence or absence of an outer shell (supercapside); 5) antigenic structure; 6) phenomena of genetic interactions; 7) a circle of susceptible hosts; 8) geographical distribution; 9) internal or cytoplasmic localization; 10) Ethira sensitivity and detergents; 11) The path of transmission of infection.
To determine affiliation to the family of retroviruses, reverse transcriptase enzyme is necessarily taken into account.
Viruses causing infectious processes in humans are included in the composition of both DNA-containing and RNA-containing viral families (see Table 1).
Table 1.
Classification and some properties of viruses
| Virus family | Type of nucleic acid | Virion size, nm | Availability supercapsida | Typical representatives |
| RNA genomic viruses | ||||
| Arenaviridae Arenavirusi | Fragmented, single-grade | 50-300 | + | Lasse Viruses, Machupo |
| Bunyaviridae Buignavirus | Fragmented, single-grade, ring | 90-100 | + | Gemorrhagic fever and encephalitis viruses |
| Caliciviridae Calicivirus | Single-grades | 20-30 | - | Hepatitis E virus, human caliciviruses |
| Coronaviridae Coronavirus | Single-grated (+) RNA | 80-130 | + | Coronavirus man |
| Orthomyxoviridae orthomyxoixomes | Single-graded, fragmented (-) RNA | 80-120 | + | Influenza viruses |
| Paramyxoviridae Paramyxo-viruses | Single-grated, linear (-) RNA | 150-300 | + | Viruses Paragrippa, Corey, Epidemic Parotitis, RS-Virus |
| Picornaviridae Picornavirus | Single-grated (+) RNA | 20-30 | - | Poliomyelitis Viruses, Koksaki, Esno, Hepatitis A, Rhinovirus |
| Reoviridae Rovirusi | bunk RNA | 60-80 | - | Rovirusi. |
| Retroviridae Retroviruses | Single-grade RNA | 80-100 | + | Cancer viruses, leukemia, sarcoma, HIV |
| Togaviridae Togavirus | Single-grated (+) RNA | 30-90 | + | Viruses of horsepower encephalitis, rubella and others. |
| Flaviviridae Flavivirus | Single-grated (+) RNA | 30-90 | + | Tick-borne encephalitis viruses, yellow fever, dengue, japanese encephalitis, hepatitis C, G |
| Rhabdoviridae Rabdigs | Single-grade (-) RNA | 30-90 | + | Warming Virus, Vesicular Stomatitis Virus |
| Filoviridae Falovirus | Single-grated (+) RNA | 200-4000 | + | Ebola Viruses, Marburg |
| DNA genomic viruses | ||||
| Adenoviridae Adenovirus | Linear, bunk | 70-90 | - | Adenoviruses of mammals and birds |
| Hepadnaviridae Hepadnavirusi | bunk, ring with a single-grade site | 45-50 | + | Hepatitis B virus |
| Herpesviridae herpesviruses | Linear, bunk | + | Viruses of a simple herpes, cytomegaly, chickenpox, infectious mononucleosis | |
| Papovaviridae Popovaavirus | bunk, ring | 45-55 | - | Papilloma Viruses, Polyoms |
| Poxviridae Poksvirusi | bunk with closed ends | 130-250 | + | Cupovaccine virus, Natural Phase virus |
| Parvoviridae Parvovirus | Linear, single-grade | 18-26 | - | Adino-associated virus |
4.2. The structure of viruses
In structure, two types of viral particles are distinguished - simple and complex. As part of simple virions, there are DNA or RNA and proteins. In the supercupsis complex in supercupsis contains lipids, polysaccharides.
The internal structure of ordinary and complex virus is similar, the core of the virus is a viral genome that contains from 3 to 100 or more genes.
Morphology and structure of viruses. Simple viruses have one protein shell - capsidwhich consists of capsages - protein molecules, the laying form of which determines the type of symmetry. The capsid is represented by A-spiral proteins capable of polymerization.
Sophisticated viruses have an outer shell - a supercupside located on top of the capsid. The supercupsis includes an inner protein layer - M-protein, then a more volumetric layer of lipids and carbohydrates extracted from the cell membranes of the host cell. VirusSpecific glycoproteins penetrate inside the supercupsis, forming curly protrusions (spikes, fibers) that perform a receptor function.
Distinguish 3 types of symmetry: 1) spiralwhen the capsos are stacked on the helix - the knitting structure of the nucleocapsid; 2) cubic (Ikosahedrical) when the capsos are stacked on the edges of the polyhedron (12-20-born) - the basis of the figure of the icosahedron (20-year-old). Depending on the type of regrouping and the number of subunits, the number of capsages will be equal to 30, 20, or 12. Virions with a complex capsid, constructed by more than 60 capsages, contain groups of 5 subunits - pentamers, or from 6 subunits - hexamera; 3) mixed Symmetry type (in bacteriophages).
Capside complex and virus genome called nucleocapsid. Difficult viruses have super CupSide (Peplos). This surface shell of the virus consists of lipids and cells of cellular origin.
Viral proteins are: 1) structural; 2) nonstructural.
Among structural distinguishes: capsid - included in the captions and form a case protecting nucleic acid; supercapsida - These are glycoproteins that form the spikes on the surface of the supercupsis and perform: addressible function - recognize the sensitive cell and are adsorbed on it; attachmentproteins that interact with specific cell receptors; Proteins merge - contribute to the merger of viral and cell membranes and lead to the formation of symplasts; genomic - Have antigenic properties, participate in interaction with the cell.
Among the non-structural proteins distinguish: predecessors of viral proteins(unstable); RNA and DNA polymerase - participate in the replication of the viral genome; regulatory proteins - participate in the reproduction of the virus.
Protein functions: possess antigen and immunogenic properties; participate in cell recognition and interaction with it; Protect genomes from nucleases; Provide type of symmetry.
Lipids It is part of the supercupsis and represent a mixture of neutral phospho- and glycolipids, many of them are the products of the host cell membrane.
They determine infectiousness, sensitivity or resistance to ether; Stabilize a viral particle.
Carbohydrates Participated supercupside glycoproteins. Carbohydrates and lipids are an integral part of hemagglutinin, which causes gluing erythrocytes and has antigenic specificity.
Distinguish virion and virusinduced Enzymes of viruses. Virive includes transcription and replication enzymes (DNA and RNA polymerase); reverse transcriptase (in retroviruses), ATP-Aza, endo- and exonucleases, neuraminidase.
Virusinducted enzymes include only information in the viral genome, and they appear in the cell. These are RNA polymerases of Toga, Ortho-, Pecorno- and Paralims; and DNA polymerase in Poks and herpesviruses.
Nucleic acidsprovide hereditary signs; are keepers of genetic information; We are necessary for reproduction of viruses, many of them can cause an infectious process independently, their penetration into the cell.
Viral DNA.Molecular weight is 1.10 6 -1.10 8 Dalton. DNA can be single or bunk, fragmented and superpioralized, linear or ring, contains several hundred genes. In each DNA thread there are nucleotide sequences, and at the ends there are direct or inverted (rotated at 180 o) repeats, which are markers to distinguish between virus DNA from cell. These repeats provide DNA ability to close to the ring for subsequent replication, transcribed and embedding in the cellular gene. Genetic information infectious DNA is broadcast on mRNA in a cell using polymeraz.
Viral RNAit may be single and bunk, linear, ring, fragmented. RNA-containing viruses, genetic information is encoded in the RNA in the same code as in DNA of all other viruses and cellular organisms. Viral RNA in its chemical composition does not differ from RNA of cellular origin, but are characterized by a different structure.
Along with the typical of all RNA, a single-dimensional form in a number of viruses has a bunk RNA. In the composition of single-type RNA, there are spiral sections of the type of DNA double spiral, resulting from mating concrete nitrogen bases. Viruses with single-grade RNA are divided into 2 groups: (+) RNA (positive genome) and (-) RNA (negative genome). Viral (+) RNA infectious and has functions of information RNA. It can convey genetic information on ribosomes like IRNA. Viruses with a negative genome do not have infectiousness, because The RNA thread (-) performs only the hereditary function and does not possess the IRNK function. In an infected cell on a matrix of viral genomic RNA using an enzyme transcriptase, a synthesis of RNA-complementary genome is carried out.
Nights (+) RNA viruses Unlike (-) RNA have special ends in the form of "caps" for specific recognition of ribosomes.
The pathogenicity of viruses is due to the totality of their properties: the ability to penetrate the macroorganism, bind to cell membranes and penetrate the cell, control the metabolism and the white cell function, to ensure the transcription and replication of its own genome and carry out the entire reproduction cycle of viruses. All these properties depend on the genome of viruses and the presence of appropriate structural proteins and enzymes. The reproduction of viruses leads to the development of pathology: cytopathogenic (destroying) action, the development of inflammation, damage to various cells and tissues.
7th grade
VII . Reflection
Think and tell me: Do you need knowledge gained today at the lesson? Why?
application
Concept of viruses
Viruses - intracellular organisms
Viruses are nucleic acid molecules (DNA or RNA) enclosed in protective protein shell (capsid). Viruses contain only one type of nucleic acid: either DNA or RNA.
Viruses are one of the most common forms of the existence of organic matter on the planet of the number: Water of the World Ocean contain a colossal amount of bacteriophages (about 10 11 Particles per milliliter of water).
History of studying viruses
In 1852, Russian Botanist Dmitry Ivanovsky received an infectious extract from tobacco plants affected by a mosaic disease.
In 1898, the Dutchman Beierink introduced the term "virus" (from Latin - "poison" to identify the infectious nature of certain profiltrated vegetable liquids
Vital life cycle
In contrast to all organisms, viruses are not able to multiply by binary division (separated in two). Finding into a cage, the nucleic acid of the virus "causes" the cell to synthesize the components of the virus from its cellular materials. This leads a cell to the death and liberation of the formed new (subsidiary) virions, which are already able to infect other cells.
Viral diseases of plants
In plants - mosaic or other changes in the color of the leaves or flowers, the curlyness of the leaves and other changes in the form, dwarfship; Finally, the bacteria - their collapse.
Viral animal diseases
Animals viruses cause lush, plague, rabies; Insects - polyhedron, granulomatosis.
Viral diseases of man
Viral human diseases are measles, pig, flu, polio, rabies, pieces, yellow fever, trachoma, encephalitis, some oncological (tumor) diseases, AIDS, warts, herpes.
AIDS
In 1981, a new, previously not known science was the disease that was called AIDS. In 1983, a virus was opened, called HIV, causing this disease
HIV - human immunodeficiency virus, causing a disease of AIDS, acquired immunodeficiency syndrome. In this disease, there is damage to the system of cellular immunity - infectious diseases and malignant neoplasms develop, the body becomes completely defenseless before microbes.
AIDS virus contains 2 RNA molecules. It specifically binds to blood cells - leukocytes, as a result of which their functional activity is reduced.
Many confuse two completely different concepts - HIV-infected and a sick AIDS. The difference lies in the fact that a person infected with the immunodeficiency virus may remain workable for many years, a relatively healthy person. Such a person does not represent any danger to others.
Ways transfer HIV infection:
From mother to child: intrauterine, during childbirth, when feeding,
Through blood: when overflowing blood, when transplanting organs, tissues,
When using contaminated honey. Tools (syringe addict)
What is the likelihood of getting a speed? After all, B. this case The system performs the protective function is affected.
Risk groups where the probability of getting sick is quite high.
homosexuals
people leading erratic sex life
prostitutes
drug addicts
donors and recipients
What do you need to do to protect yourself from this disease?
use disposable tools
install good control over donor blood
to fight against drug addiction associated with AIDS infection.
Bacteria viruses - bacteriophages
Bacteriophages - "Bacteria Eaters. Opened in 1917 at the same time in France and England
Used in the treatment of diseases caused by some bacteria (plague, tit, dysentery)
Three main ways to combat viral diseases: each of them is valid in its own way.
1 method - vaccination .
The essence of it is reduced to the simple formula of the "Bay enemy of his arms". The virus here opposes the virus. Vaccines include immunity system. In 1885, the French scientist Louis Paster invented a vaccine against rabies. When introduced into the body, such viruses do not cause diseases, but an active immunity is created to this virus.
2 method - chemotherapy.
This is the impact of chemical preparations for viruses. The difficulty is that viruses multiply inside the cells using their systems, due to the impact on viruses leads to a violation of cell metabolism.
3 Method - Interferon.
This is a protective protein produced by cells in response to infection with viruses. It acts on the principle of stop signal and suppresses the reproduction of viruses already penetrated into the cell. Experience shows that if interferon is weakly produced, the virus diseases are heavier).
Finish phrases (writing):
1. Science of viruses is called .... .
2. Viruses dwell only in ... ....
3. Viruses are intracellular ....
5. The virus includes nucleic acid ... or .... and several proteins, forming a shell around nucleic acid.
6. The protein sheath of the virus that protects its nucleic acid from the external the impacts are called ....
7. The virus affecting bacteria is called ...
8. Science of viruses ....
(Mute on the estimation scale: "5" - 8 replies; "4" - 6-7 replies; "3" - 4-5 replies; "2" - less than 2 responses).
Virus (from lat. Virus - poison) is the simplest form of life, a microscopic particle, which is a nucleic acid molecules (DNA or RNA, some, for example, mimiviruses, have both types of molecules) enclosed in a protein sheath and capable of infecting live organisms . From other infectious agents, viruses feature capsid. Viruses, with rare exception, contain only one type of nucleic acid: either DNA or RNA. Earlier, the prions were also mistaken for viruses, but subsequently it turned out that these pathogens are special proteins and do not contain nucleic acids.
For the first time, the existence of a virus (as a new type of causative agent of diseases) proved in 1892 by Russian scientist D. I. Ivanovsky. After many years of research of diseases of tobacco plants, in the work dated 1892, D. I. Ivanovsky comes to the conclusion that the tobacco mosaic is caused by "bacteria passing through the Shambherlan filter, which, however, cannot grow on artificial substrates."
Five years later, when studying the diseases of cattle, namely, the foot and a similar filtering microorganism. And in 1898, when reproducing experiments by D. Ivanovsky, Dutch Botany M. Beiyintsky, he called such microorganisms with "filtering viruses". In abbreviated form, this name and began to designate this group of microorganisms.
In 1901, the first viral disease of man was found - yellow fever. This discovery was made by the American military surgeon of W. Reed and his colleagues.
In 1911, Francis Raus proved the viral nature of cancer - Rauys's sarcoma (only in 1966, 55 years later, he was awarded for this discovery of the Nobel Prize in physiology and medicine).
In subsequent years, the study of viruses played a crucial role in the development of epidemiology, immunology, molecular genetics and other biology sections. Thus, the experiment, Hershi-Chase, became a decisive proof of the role of DNA in the transfer of hereditary properties. In different years, at least six Nobel Prizes on Physiology and Medicine and the three Nobel chemistry premiums were awarded for research directly related to the study of viruses.
In 2002, the first synthetic virus (poliomyelitis virus) was created in the University of New York University.
Simply organized viruses consist of nucleic acid and several proteins forming around her shell - capsid. Examples of such viruses is a tobacco mosaic virus. Its capsid contains one kind of protein with a small molecular weight. Completely organized viruses have an additional shell - protein or lipoprotein; Sometimes in the outer shells of complex viruses, in addition to proteins contain carbohydrates. An example of complex organized viruses serve as influenza and herpes. Their outer shell is a fragment of a nuclear or cytoplasmic membrane of the host cell, from which the virus is coming out into the extracellular medium.
Viral particles (viriomines) are a protein capsule - capsid containing the virus gene represented by one or more DNA or RNA molecules. The capsid is built of capsages - protein complexes, in turn, from protéers. Nucleic acid in the protein complex is denoted by the term nucleocapside. Some viruses also have an outer lipid shell. The dimensions of various viruses fluctuate from 20 (parvoviruses) to 500 (mimivirus) and more nanometers. Virions often have a proper geometric shape (Ikosahedron, cylinder). Such a structure of the capsid provides for the identity of the bonds between the components of its proteins, and, therefore, can be built from standard proteins of one or more species, which allows the virus to save place in the genome. 2. Custom characteristic of viral diseases.
Viral diseases are human diseases arising in connection with the penetration of the human body and the development of various viruses in them, which are the smallest forms of life consisting of a nucleic acid molecule, a carrier of genetic information surrounded by a protective sheath of proteins.
The virus breeds, feeding the contents of the cell, as a result of which the cell is destroyed dies.
Upon epidemiological characteristics, viral diseases are divided into anthroponous viral diseases, that is, those with which only a person (for example, poliomyelitis) and zooanthroponous viral diseases are sick - which are transmitted from animals to man (for example rabies).
According to the nature of the distribution, viral diseases can be transmitted by air-droplet, with contacts, including sexual relations (STD), through public items, food, etc.
Viruses can affect the cells of various human organs, therefore the virus diseases of the skin, the sexual sphere (), respiratory tract and the respiratory organs (lung disease), virus diseases of the intestine, liver, diseases of the oral mucosa (herpes), eyes, etc. are distinguished.
Antiviral drugs with clinically proven effectiveness, there is much less than antibiotics. Based on the peculiarities of preferential use, antiviral drugs can be divided into several groups: anticherine, anti-coaliviral, anti-hygospose and possessing an extended spectrum of activity.
Classification of antiviral drugs *
* In addition to antiretroviral drugs.
Viruses are open to Russian Botany D.I. Ivanovo (1864 - 1920) in 1892 in the study of the mosaic disease of Tobacco leaves. The term "virus" was first proposed in 1898 by the Dutch scientist M. Beierinki (1851-1931).
Currently, about 3000 different types of viruses are known.
The dimensions of the viruses range from 15 to 350 nm (the length of some threads reaches 3,000 nm; 1 nm \u003d 1 · 10 -9 m), i.e. Most of them are not visible in the light microscope (submicroscopic) and their study has become possible only after the invention of the electron microscope.
In contrast to all other organisms, viruses do not have a cellular structure!
Mature viral particle (i.e. extracellular, resting - virion) It is very simple: it consists of one or more nucleic acid molecules constituting corevirus and Protein Shell (capsid) - these are the so-called simple viruses.
Difficult viruses (eg, herpes. or influenza) Besides, capsid and nucleic acid proteins contain additional lipoprotechnic membrane (Shell, supercupside formed from plasma membrane host cells), various carbohydrates and enzymes (Fig.3.1).
Enzymes contribute to the penetration of viral NK into the cell and the output of the formed virions on Wednesday ( neuraminidasis mixing, ATP-AZA and lizozyme Some phages, etc.), and also participate in the transcription and replication process of viral NK (various transcriptase and replicase).
White shell Protects nucleic acid from various physical and chemical impacts, and also prevents cell enzymes to penetrate it, thereby preventing its splitting (protective function). Also, in the composition of the capsid there is a receptor, a complementary receptor of the infected cell - viruses affect a strictly defined range of owners (determinant function).
Virions many plant viruses and rows of phages have spiral The capsid in which protein subunits (capsamers) are stacked around the axis. For example, VTM ( tobacco Mosaic virus) It has the shape of sticks with a diameter of 15 - 17 nm and up to 300 nm long (Fig. 3.2.). Inside its capsid there is a hollow channel with a diameter of 4 nm. The genetic material VTM is a single-stranded RNA, tightly laid in the groove of a spiral capside. For virionov With a spiral capside, a high protein content (90 - 98%) is characterized in relation to nucleic acid.
Capsides of virions of many viruses (for example, adenovirus, herpes virus, yellow Mosaic Virus Turnip - VZHMT) have the shape of a symmetric polyhedron, most often of the ikosahedron (polyhedron with 12 vertices, 20 triangular faces and 30 ribs). Such capsids are called isometric(Fig. 3.3.). In such virions, the protein content is about 50% relative to the NK.
There is always one type of nucleic acid (either DNA or RNA) in the virus, so all viruses are divided into DNA-containing and RNA-containing. Nucleic acid molecules in the virion can be linear (RNA, DNA) or have a rings shape (DNA). Moreover, these nucleic acids may consist of one chain or of two. Viral NK has from 3 to 200 genes.
The nucleic acid of the virus combines the functions of both acids (DNA and RNA) - it is storage and transfer of hereditary information, as well as control of protein synthesis.
