Amazing facts about viruses
The virus (Latin virus - poison) is a non-cellular infectious agent that can be reproduced only within living cells. Viruses affect all types of organisms, from plants and animals to bacteria and archaea (viruses of bacteria are usually called bacteriophages). Viruses that can replicate only in the presence of other viruses (viruses-satellites) are also found.
Since the publication in 1892 of an article by Dmitry Ivanovsky describing the non-bacterial pathogen of tobacco plants and the discovery of the tobacco mosaic virus in 1898 by Martin Beyerinck, more than 6,000 species of viruses have been described in detail, although it is estimated that there are more than one hundred million. Viruses are found in almost every ecosystem on Earth, they are the most numerous biological form. The study of viruses deals with the science of virology, the division of microbiology.
While the virus is in the extracellular environment or in the process of infection of the cell, it exists as an independent particle. Viral particles (virions) consist of two or three components: a genetic material in the form of DNA or RNA (some, for example, mimiviruses, have both types of molecules); protein coat (capsid), protecting these molecules, and, in some cases, additional lipid envelopes. Presence of the capsid distinguishes viruses from virus-like infectious nucleic acids - viroids. Depending on what type of nucleic acid the genetic material is represented, DNA-containing viruses and RNA-containing viruses are isolated; on this principle the classification of viruses by Baltimore is based. Previously, the viruses were erroneously referred to prions, but later it turned out that these pathogens are special infectious proteins and do not contain nucleic acids. The form of the virus varies from simple spiral and icosahedral to more complex structures. The average virus size is about one hundredth the size of the average bacterium. Most viruses are too small to be clearly distinguishable under a light microscope.
Viruses are obligate parasites, since they can not breed outside the cell. Outside the cell, the viral particles show no signs of being alive and behave like particles of biopolymers. From living parasitic organisms, viruses are characterized by a complete lack of basic and energy metabolism and the absence of the most complex element of living systems - the apparatus of translation (protein synthesis), the degree of complexity of which exceeds that of the viruses themselves
The appearance of viruses on the evolutionary tree of life is unclear: some of them could have been formed from plasmids, small DNA molecules, capable of transmitting from one cell to another, while others could have come from bacteria. In evolution, viruses are an important means of horizontal gene transfer, which causes genetic diversity. Some consider viruses a special form of life, since they have genetic material, are able to create similar viruses, and evolve through natural selection. However, viruses lack important characteristics (such as cellular structure), without which they can not be attributed to the living. Since they have some, but not all, properties, viruses are described as "organisms on the edge of life".
Viruses spread in many ways: plant viruses are often transmitted from plant to plant by insects that feed on plant juices, for example, aphids; animal viruses can be spread by blood-sucking insects, such organisms are known as vectors. The influenza virus spreads by air-drop by coughing and sneezing. Norovirus and rotavirus, usually causing viral gastroenteritis, are transmitted by the fecal-oral route by contact with contaminated food or water. HIV is one of several sexually transmitted viruses and transfusions of infected blood. Each virus has a specific host specificity, determined by the types of cells that it can infect. The range of hosts may be narrow or, if the virus affects many species, is wide.
In animals, viral infections cause an immune response, which most often leads to the destruction of the pathogenic virus. The immune response can also be caused by vaccines that give active acquired immunity against a specific viral infection. However, some viruses, including the human immunodeficiency virus and pathogens of viral hepatitis, manage to escape from the immune response, causing a chronic illness. Antibiotics do not work for viruses, but several antiviral drugs have been developed.
Are there really giant viruses, the size of which exceeds the size of the bacteria? Is it true that 2/5 of human DNA consists of the remains of ancient viruses that infected our ancestral cells at different stages? It will be really interesting ...
Plant viruses are harmless to animals, and most animal viruses are harmless to humans.
Viruses are not living beings. They do not have cells, they do not know how to convert food into energy, and without a "master" they are just small clots of chemicals. Viruses are also not something dead - they have genes, they multiply, for them the processes of natural selection operate.
It is believed that approximately 2/5 of human DNA consists of the remains of ancient viruses, which in different stages infected the cells of our ancestors.
To date, more than 2000 variants of the influenza virus are known, which differ in antigenic spectrum.
In 1859, an Australian farmer took rabbits from England to create a small population and hunt them.
The absence of natural enemies and ideal conditions for life and reproduction all year round caused the uncontrolled growth of the rabbit population, which led to the disappearance of many species of native plants.
The rabbits were tried to fight by shooting, blowing holes, poisons, building net barriers, but everything is useless. Finally, in the middle of the 20th century, the Myxomatosis virus spread among them, which reduced the population from 600 million to 100 million. However, surviving individuals acquired genetic resistance to the virus and again began to multiply actively.
Viruses, undoubtedly, are the most numerous biological objects on the Earth, and by this index they surpass all organisms taken together.
Large-scale viruses are called mamaviruses.
Their size often exceeds the size of even some bacteria.
Such viruses have virus-satellites.
The so-called mimivirus is named so because it imitates the behavior and structure of the bacterium.
Some experts believe that it is an intermediate link between bacteria and viruses, others believe that this is a separate form of life.
This virus is characterized by the most voluminous and complex set of DNA among all viruses.
In 1992, scientists followed the path of the source of pneumonia that erupted in England - it turned out that it was a virus that hid inside an amoeba that lives in the towers of a cooling tower (cooling tower). It was so large that at first scientists took it for a bacterium.
Amoeba for viruses are original sandboxes and free dining rooms - they absorb large objects within their reach and are a source of nutrients for bacteria that exchange genes with other bacteria and viruses inside the amoeba.
Braconids instead of poison introduce their victims a virus that suppresses the immune system of the victim.
Depressed immunity allows the larva to develop a parasitic larva within the victim.
Biologists found that the virus is more than a hundred million years old, and most likely it merged with wasp DNA.
When an embryo is formed inside a woman, the immune system recognizes a new generation as something foreign.
Thanks to the DNA of the virus that encodes proteins, the fetus is not threatened by immunity.
Via Internet & wiki