In the article, we will talk about the history of the discovery of viruses. This is an interesting topic, which in the modern world is not given so much attention, but in vain. First, we will figure out what the virus itself is, and then talk about other aspects of this issue.
Virus
A virus is a non-cellular infectious organism that can multiply only inside living cells. By the way, from Latin this word is translated literally as "poison". These formations can affect all types of living organisms, from plants to bacteria. There are also viruses that can multiply only inside their other brethren.
Study
The beginning of research was laid in 1892. Then Dmitry Ivanovsky published his article in which he described the pathogen of tobacco plants. In 1898, the tobacco mosaic virus was discovered by Martin Beyerink . Since that time, scientists have already described about 6,000 different viruses, although they believe that there are more than 100 million of them. Note that these formations are the most numerous biological form that is present in any ecosystem on Earth. Virology is engaged in their study, namely, the microbiology section.
Short description
Note that while the virus is outside the cell or in the process of nucleation, it is an independent particle. Usually consists of three components. The first is the genetic material that is represented by DNA or RNA. It should be noted that some viruses can have two kinds of molecules. The second component is the protein membrane, which protects the virus itself and its lipid membrane. By its presence, viruses are distinguished from similar infectious bacteria. Depending on the type of nucleic acid, which is essentially a genetic material, DNA-containing and RNA-containing viruses are separated. Prions were previously referred to viruses, but then it turned out that this erroneous opinion is ordinary pathogens, which consist of infectious material and do not contain nucleic acids. The shape of the virus can be very diverse: from spiral and ending with much more complex structures. The size of these formations is approximately one hundredth of a bacterium. However, most viruses are so small that they cannot be clearly seen even with a light microscope.
Life form
In terms of life form, such organisms are obligate parasites, since they cannot reproduce outside the cell. Being in such an environment, particles do not show any signs of living organisms. Viruses differ from parasites in that they completely lack energy and basic metabolism, as well as an important element of all living systems - protein synthesis, the complexity of which exceeds even the structure of the virus.
Appearance
The history of the discovery of the virus is silent about how they appeared on the evolutionary tree. This is indeed a very interesting question that has not yet been sufficiently studied. It is believed that some viruses could be formed from small DNA molecules that could be transmitted between cells. There is another option that viruses come from bacteria. Moreover, due to their evolution, they are an important element in horizontal gene transfer and provide genetic diversity. Some scholars consider such formations to be a distinctive life form according to some criteria. Firstly, there is genetic material, the ability to reproduce and evolve naturally. But at the same time, viruses do not have very important characteristics of living organisms, for example, the cellular structure, which is the main property of all living things. Due to the fact that viruses possess only a part of the characteristics of living things, they are classified as existing on the edge of life.
Spread
Viruses can spread in different ways; there are many different ways. They can be transmitted from plant to plant with the help of insects that feed on plant juices. An example is aphids. In animals, viruses can spread through blood-sucking insects that transmit bacteria. As we know, the flu virus spreads in the air when sneezing and coughing. For example, rotavirus and norovirus can be transmitted by contact with contaminated food or liquid, that is, by the fecal-oral route. HIV is one of the few viruses that can be transmitted by blood transfusion and through sexual contact.
Each new virus has a certain specificity in relation to its hosts. In this case, the circle of hosts can be narrow or wide, depending on how many cells were able to hit. Animals respond to infection with an immune response, which means that pathogens are destroyed. Viruses as a life form are quite adaptable, so destroying them is not so simple. In humans, a vaccine against specific infections can serve as an immune response. However, some organisms can pass through the human internal security system and cause chronic illness. This is a human immunodeficiency virus and various hepatitis. As you know, antibiotics cannot affect such organisms, but, despite this, scientists have developed effective antiviral drugs.
Term
But before talking about the history of the discovery of viruses, let's talk about the term itself. As we know, literally the word translates as "poison." It was used in 1728 to determine the body that can cause an infectious disease. Before Dmitry Ivanovskiy discovered viruses, he coined the term “filterable virus” by which he understood a pathogenic agent of a non-bacterial nature that can undergo various filters in the human body. Also, the famous term "virion" was coined in 1959. It means a stable viral particle that has left the cell and can itself further infect.
Research history
Viruses in microbiology have become something new, but data on them has accumulated gradually. As a result of the development of science, it became clear that not all viruses are caused by pathogens, microscopic fungi or protists. Note that the researcher Louis Pasteur could not find an agent that causes rabies. Because of this, he suggested that he was so small that it was impossible to examine it under a microscope. In 1884, Charles Chamberlain, a well-known microbiologist from France, invented a filter whose pores are much smaller than bacteria. With this tool, bacteria can be completely removed from the liquid. In 1892, the Russian microbiologist Dmitry Ivanovsky used this apparatus to study the species, which later became known as the tobacco mosaic virus. The scientist's experiments showed that even after filtration, infectious properties are preserved. He suggested that the infection could be triggered by the toxin that bacteria secrete. However, then the man did not further develop this idea. At that time, ideas were popular that any pathogen can be identified using a filter and grown in a nutrient medium. Note that this is one of the postulates of the theory of the disease at the level of microbes.
"Ivanovsky crystals"
Using an optical microscope, Ivanovsky observed infected plant cells. He discovered bodies like crystals, which are now called clusters of viruses. However, then this phenomenon was called "Ivanovsky crystals." The Dutch microbiologist of 1898, Martin Beyerink, repeated the experiments of Ivanovsky. He decided that the infectious material that passes through the filter is a new form of agent. At the same time, he confirmed that they can multiply only in dividing cells, but in experiments it was not revealed that they were particles. Then Martin called these particles "soluble living microbes", literally, and again began to use the term "virus". The scientist believed that viruses are liquid by nature, but this conclusion was refuted by Wendell Stanley, who proved that in essence viruses are particles. Then Paul Frosch and Friedrich Leffler found the first animal virus, namely, foot-and-mouth disease pathogens. They passed it through a similar filter.
Virus Life Cycle and Further Research
At the beginning of the last century, the English bacteriologist Frederick Tuort discovered a group of viruses that could multiply in bacteria. Now such organisms are called bacteriophages. At the same time, Canadian microbiologist Felix Derell described viruses that, when exposed to bacteria, can form a space around them with dead cells. He made suspensions, thanks to which he was able to determine the lowest concentration of the virus, at which not all bacteria die. Having made the necessary calculations, he was able to determine the initial number of viral units in suspension.
The life cycle of the virus was actively investigated at the beginning of the last century. Then it became known that these particles can have infectious properties, pass through a filter. At the same time, they need a living host for reproduction. The first microbiologists studied viruses only on plants and animals. In 1906, Ross Granville Harrison invented a unique way to grow tissue in lymph.
Breakthrough
At the same time, new viruses were discovered. Their origin has remained and remains a mystery today. Note that the discovery of the flu virus belongs to the American researcher Ernest Goodpascher. In 1949, a new virus was discovered. Its origin was unknown, but the body was able to grow on the cells of a human embryo. Thus, the first poliovirus grown on living human tissues was discovered. Thanks to this, the most important polio vaccine against poliomyelitis was created.
The image of viruses in microbiology appeared due to the invention of an electron microscope by engineers Max Knoll and Ernst Ruska. In 1935, an American biochemist conducted a study that proved that the tobacco mosaic virus consists mainly of protein. A little later, this particle was divided into a protein and RNA component. It was possible to crystallize the mosaic virus and to study its structure in much more detail. The first x-ray was obtained in the late 1930s thanks to scientists Barnal and Fenkuchen. A breakthrough in virology is in the second half of the last century. It was then that scientists discovered more than 2,000 different types of viruses. In 1963, the discovery of the hepatitis B virus by Blumberg. In 1965, the first retrovirus was described.
Summing up, I want to say that the history of the discovery of viruses is very interesting. It allows you to understand many processes and understand them in more detail. However, at least a superficial idea must be in order to keep up with the times, because progress is developing by leaps and bounds.