Who first discovered the virus?

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At the end of the 19th century, Dmitry Ivanovsky was the first to discover the virus. However, it was not until the beginning of the 20th century that scientists discovered viruses with many other types. And with the invention of the electron microscope, scientists were able to clearly see the structure of viruses and study their evolution more deeply.

1. The first person to find the virus

Dmitri Ivanovsky was the first to discover the virus. He was born in the village of Nizy, Gdov Uyezd. He studied at Saint Petersburg University under Andrei Famintsyn. In 1887, when Ivanovsky was sent to Ukraine and Bessarabia to investigate a disease in tobacco plants, which caused great damage to the plantations at the time. Three years later, Ivanovsky was again sent to check for the occurrence of a similar disease in tobacco, this time rife in the Crimea. Ivanovsky discovered that both incidents were caused by an extremely small infectious agent, capable of penetrating through Chamberland filters, something bacteria could never do. Ivanovsky described his findings in a paper (in 1892) and a thesis (in 1902). After that, he moved to other jobs in Warsaw and Rostov-on-Don.
Six years later, in 1898, a Dutch biologist named Martinus Beijerinck carried out similar experiments himself, he claimed to have found a new type of infectious organism and named it "virus". Neither Ivanovsky nor Beijerinck understood that viruses were molecules called virions; Ivanovsky thought it was a toxin produced by bacteria. It was not until the advent of electron microscopes in the 1950s that it was discovered that the tobacco mosaic virus is a small hollow rod, formed by a single helical RNA strand, enclosed surrounded by a protein coat.

2. Origin of Virus

Viruses have existed since time immemorial. Molecular studies have shown a relationship between viral systems infecting from one of three domains of life, suggesting that viral proteins predate life's divergence. This indicates that some viruses emerged early in the evolution of life, and that they may have arisen many times. It has been suggested that new groups of viruses have continuously emerged at all stages of evolution, often through shifts between the structure of the replicated genes and the source genome.
There are three classical theories about the origin of viruses and how they evolved:
First hypothesis about viruses : Viruses evolved from complex molecules of proteins and nucleic acids before cells first appeared on the earth. According to this hypothesis, the virus contributed to the increase of cell survival. This is confirmed by the idea that all viral genomes encode proteins with no cytoplasmic homology. The first hypothesis about viruses has been rejected by some scientists because it violates the definition of viruses, according to which they need a host cell to replicate. Reduction hypothesis (degeneration hypothesis): Viruses used to be small cells that parasitized larger cells. The discovery that giant viruses have similar genetic material to parasitic bacteria is the basis for this hypothesis. However, this hypothesis does not explain why even the smallest cellular parasites do not resemble viruses in any way. Escape hypothesis (vague hypothesis): Some viruses evolve from DNA or RNA molecules that "escape" from the genomic system. This does not explain why the structures for the virus are unique and not found anywhere in the cells. Nor does it explain the complex outer envelopes of viral proteins and other structures of viral molecules. However, virologists are in the process of re-evaluating all of these hypotheses.
Coevolution hypothesis (Bubble theory): In the early stages, a community of replicators (pieces of genetic information capable of self-replicating) exist near food sources. This food source also produces lipid-like molecules that self-assemble into vesicles that can hold copies. Near the food source clones thrive, but farther away only the undiluted resources are inside the bags. Thus, evolutionary pressure can push clones along two developmental pathways: fusing with a vesicle, producing cells; and enter the pocket, use its resources, multiply and leave another pocket, giving rise to the virus. The origin hypothesis of genetics: Based on analyzes of the evolution of viral replication modules and structure, a genetic scenario for the origin of viruses was proposed in 2019. According to this hypothesis, viral replication modules are derived from the primitive gene pool, although their subsequent long evolution involved multiple translocations by genes copied from the host host. cell. In contrast, genes encoding major protein structures evolved from functionally diverse host proteins throughout the evolution of the viral world. This scenario differs from the traditional three scenarios but combines the features of the first hypothesis and the exit hypothesis. One of the problems in studying the origin and evolution of viruses is the very high rate of virus mutations, especially in the case of retroviral RNA infections such as HIV/AIDS. However, a recent study, based on a comparison of the protein folding structure of viruses, is providing some new evidence. Fold Super Family (FSF) are proteins that show similar folding structures independent of amino acid sequence and have found evidence of virology. Thus, the virus was found to be capable of being divided into 4 FSFs. The viral proteome still contains traces of ancient evolutionary history, which is still being studied today. The study of the FSF protein revealed the existence of ancient cell lines common to both cells and viruses before the emergence of the 'last universal cell ancestor' that gave rise to modern cells. Evolutionary pressure to reduce genome and particle size may have eventually reduced vero cells to modern viruses, while other coexisting cell lines eventually evolved into modern cells. . Furthermore, the long genetic distance between RNA and FSF DNA suggests that the RNA world hypothesis may have new experimental evidence, with a long intermediate stage in the evolution of cell life.
A final exclusion of a hypothesis about the origin of viruses is very difficult to make on earth because viruses and cells interact everywhere. Therefore, from a biological point of view, it has been proposed that on celestial bodies such as Mars not only cells but also traces of virions or former viroids should be actively searched. If only traces of virions but no cells were found on another celestial body, this would be a strong indication of the virus first hypothesis.

3. History of virology

Virology is the study of viruses and the infections they cause - beginning in the late 19th century. Although Louis Pasteur and Edward Jenner developed the first vaccines to protect fight the virus infection, but they don't know that the virus exists. The first evidence of the virus's existence came from experiments with filters small enough to trap bacteria. In 1892, Dmitri Ivanovsky used one of these filters to show that sap from a diseased tobacco plant still infects a healthy tobacco plant despite being filtered. Martinus Beijerinck's infectious substance is named for the virus and this discovery is considered the beginning of virology.
Subsequent discoveries, along with the work of Frederick Twort and Félix d'Herelle on part of the properties of phages, further catalyzed the field. By the early 20th century, scientists had discovered many viruses. In 1926, Thomas Milton Rivers defined viruses as parasites. Viruses were shown to be molecules, not liquids, by Wendell Meredith Stanley. In 1931, the invention of the electron microscope allowed scientists to clearly see the structure of viruses.

4. Virus evolution

Virus evolution is an area of ​​evolutionary biology and virology that focuses on the study of virus evolution. Viruses have short generation times, and many viruses, especially RNA, have a relatively high mutation rate (on the order of one point or more mutation per genome per replication loop). This elevated mutation rate, when combined with natural selection, allows viruses to rapidly adapt to changes in their host environment. Also, most viruses multiply very quickly, so any mutated gene can be passed on to generations quickly. Although the ability to mutate and evolve can vary depending on the virus (double-stranded DNA, double-stranded RNA, single-stranded DNA, etc.), viruses are, in general, highly mutable.
Virus evolution is an important aspect of the epidemiology of viral diseases such as influenza (influenza virus), AIDS (HIV), and hepatitis (eg, HCV). The rapid mutation of the virus also makes it difficult to develop vaccines and antiviral drugs, as resistance mutations often appear within weeks or months of starting treatment. One of the main theoretical models applied to virus evolution is the quarkpecies model. Define a quarkpecies as a group of closely related viral strains that compete in the environment.

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References: en.wikipedia.org, lindahall.org, britannica.com.

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