roccoschili Chapter 616 Virus
Chapter 616 Virus
Key Information Concept Introduction Classification of Viruses Application of Virus Concept of Virus Biology Concept This entry is polysemous, with a total of 16 meanings. Virus is a small individual, simple structure, containing only one type of nucleic acid (DNA or RNA), and must be present in living cells. A non-cellular organism that is parasitic and reproduces.Basic information Chinese name of virus Foreign name Virus Kingdom Virus kingdom includes mimetic viruses, viroids and virions Living conditions Live host cell mode of transmission Infection Application of vaccines, cell engineering, genetic engineering Characteristics Autonomous replication Define a unique infectious agent Key information Concept Introduction Application of Classifying Viruses Concept Catalog of Viruses
Viruses are a non-cellular life form. They are composed of a long chain of nucleic acids and a protein shell. Viruses do not have their own metabolic machinery or enzyme systems.Therefore, once the virus leaves the host cell, it becomes a chemical substance without any life activity and cannot reproduce independently.Once it enters the host cell, it can use the material and energy in the cell as well as the ability to replicate, transcribe and translate to produce a new generation of viruses just like it based on the genetic information contained in its own nucleic acid.
Concept introduction
Biological viruses in the narrow sense are a unique infectious agent. They are tiny organisms that can use nutrients from host cells to autonomously replicate their own DNA, RNA, proteins and other life components.Viruses in a broad sense are much more complex, including mimetic viruses, viroids, and virions. Among them, mimetic viruses and viroids are just a simple ssRNA chain, and a virion is an enzyme-like protein molecule.Therefore, it is difficult to have a definite and clear definition of biological viruses.
Biological viruses, whether they are virulent phages or mild phages, must be able to replicate and reproduce in living host cells. They use the nucleotides and amino acids of the host cells to autonomously synthesize some of their own components and assemble the next generation of individuals.and achieve their goals.
HIV
The replicated biological virus lyses the host cell and is released to infect new host cells.
Although biological viruses can bring certain benefits to humans, for example, phages can be used to treat some bacterial infections; insect viruses can be used to treat and prevent some agricultural diseases and insect pests, etc., they are also very harmful, such as HIV, rabies virus, etc., which have brought to humans Risk to life; influenza virus, hepatitis virus, etc. can bring diseases; TMV, potato virus Y can cause property damage to people.
Viruses are tiny organisms that can spread among other organisms and infect organisms (in fact, because viruses themselves cannot metabolize, they cannot be said to be living organisms to a certain extent).The term "virus" is sometimes used to describe those organisms that spread and infect eukaryotes; the terms "phage" or "phagosome" are sometimes used to describe those organisms that spread among prokaryotes.The origin of the virus is not entirely clear.
Basic structure of viruses:
Viruses [biological concept]
The protein shell of the virus is called the capsid, and the genetic material is mostly RNA or DNA.Capsids and nucleic acids
The molecules are collectively called nucleocapsids.But taking HIV as an example, the surface of the virus is also wrapped with a cell membrane and spike structures similar to the cell membrane, which together with the capsid determine the specificity of the virus.There are also some enzymes: such as reverse transcriptase.
Category
Viruses are not only divided into plant viruses, animal viruses and bacterial viruses.Structurally, they are also divided into: single-stranded RNA viruses, double-stranded RNA viruses, single-stranded DNA viruses and double-stranded DNA viruses.
The life process of a virus is roughly divided into five steps: adsorption, injection (genetic material), synthesis (reverse transcription/integration into host cell DNA), assembly (using host cells to transcribe RNA, translate proteins and then assemble), and release.
Because the virus will shorten the distance between cells, it is easy for the cells to fuse to form multinucleated cells, which will then lyse.
Virus Applications
1. Use inactivated viruses as vaccines
2. Used as vector in genetic engineering
3. Inducement for cell fusion in cell engineering (inactivated virus)
The latent period of the virus: The viral gene replicates as the host cell replicates and is not expressed. At this time, the number of viruses in the cell does not increase significantly.
Virus concept
Viruses are special organisms that have no cellular structure.Their structure is very simple, consisting of a protein shell and genetic material inside.Viruses cannot survive independently and must live within the cells of other organisms. Once they leave living cells, they will not show any signs of life activity.
Individual viruses are so tiny that most of them can only be seen under an electron microscope.
Key Information
Introduction to viruses
virus discovery
Virus classification
related information
culture isolation
参考资料
Pathogen
Microorganisms that cause infectious diseases in humans or animals
This entry is polysemous, with a total of 2 meanings
Pathogens refer to microorganisms (including bacteria, viruses, rickettsiae, fungi), parasites or other vectors (microbial recombinants include hybrids or mutants) that can cause infectious diseases in humans, animals and plants. [1]
Basic Information
Chinese name
Pathogen
释义
Microorganisms that can cause infectious diseases in humans or animals
Foreign name
pathogens
Discovery time
1840,
discoverer
Semmelweis
kind
microorganisms or other agents
Introduction to viruses
Pathogen is a general term for microorganisms and parasites that can cause disease.Microorganisms account for the vast majority, including viruses, chlamydia, rickettsiae, mycoplasma, bacteria, spirochetes and fungi; parasites mainly include protozoa and polyps.Pathogens are parasitic organisms, and their natural hosts are animals, plants and humans.There are more than 400 kinds of microorganisms that can infect humans, and they are widely found in the human mouth, nose, pharynx, digestive tract, genitourinary tract, and skin.
Each person may be infected by more than 150 pathogens in his or her lifetime, which do not cause disease under normal conditions of human immune function. Some are even beneficial to the human body. For example, intestinal flora (E. coli, etc.) can synthesize a variety of vitamins.The existence of these flora can also inhibit the reproduction of some highly pathogenic bacteria, so these microorganisms are called normal microflora (normal flora). However, when the body's immunity is reduced, the balanced relationship between humans and microorganisms is When destroyed, normal flora can also cause disease, so they are also called opportunistic pathogens (opportunistic pathogens).Whether the body becomes ill after being invaded by a pathogen is, on the one hand, related to its own immunity, and on the other hand, it also depends on the pathogenicity of the pathogen and the number of invaders.Generally, the greater the number, the greater the likelihood of disease.Especially pathogens with weak pathogenicity require a larger number to cause disease.A small number of microorganisms are quite pathogenic and can cause disease with just a slight infection, such as plague, smallpox, rabies, etc.
Deer mice are natural hosts for several known and emerging zoonotic pathogens, including Borrelia burgdorferi, deer tick virus (DTV), and novel hantaviruses that cause hantavirus pulmonary syndrome (HPS). Viruses (SNV).
virus discovery
The first person in history to confirm the existence of a pathogen was the Hungarian obstetrician Ignaz Semmelweis in the 1840s.He found that relatively wealthy women in the hospital who were delivered by doctors had mortality rates several times higher than poorer women who were delivered by obstetric nurses.From his observations, he determined that the difference in mortality between the two was related to the cleanliness of the environment.
Pathogen
In 1846, the Hungarian physician Semmelweis applied systematic epidemiological investigation methods to study the outbreak of puerperal fever in a hospital in Vienna.At that time, he found that in the ward he was responsible for: the fatality rate of puerperal fever among women who were delivered by obstetricians and medical students was 8.3%; the mortality rate for women who were delivered by midwives was only 2%.After analyzing the cause of the infection, he believed that if doctors touch other mothers with their hands after examining the corpses that died of puerperal fever, other mothers will also be infected. However, midwives do not perform autopsy, but deliver babies. The maternal mortality rate is lower, so he asked everyone to wash their hands carefully with bleaching powder before coming into contact with the mother, until there is no corpse smell on their hands.This move reduced the mortality rate from puerperal fever from approximately 10% to 1.5%. In 1861, based on his clinical observations and practice, Semmelweis published a book on puerperal fever.Unfortunately, his views were not accepted by the authorities at the time.Semmelweis's measures were not well adopted.His colleagues refused to accept that their hands were vehicles for disease transmission, and they dismissed his theory.Semmelweis's academic value was reduced and his hospital privileges were restricted.He left Vienna and went to Budapest, where he made the same observations, but again he was dismissed.In the end, he was even sent to a mental hospital... In extreme despair, in order to prove his point, he deliberately cut off his index finger during an autopsy on a corpse that died of puerperal fever in 1865 and died as a result. .
Pathogen
Virus classification
Determining which biosafety level a pathogen belongs to is based on experimental operations. The operations on the pathogen are usually related to the growth status of the pathogen required for identification or typing, as well as the quantity and concentration of the pathogen.If handling clinical samples poses less risk to workers than handling culture samples, it is recommended that a lower biosafety level be established.On the other hand, additional precautions may be required if the experimental procedures involve larger sample volumes and/or higher concentrations ("production quantities") of pathogen preparations, may generate aerosols, or are inherently hazardous. , and improve the level of primary and secondary anti-proliferation devices. A “production quantity” is a volume or concentration of an infectious agent that is significantly in excess of that typically required for identification and typing.As in large-scale fermentation, production of antigens and vaccines, and various commercial and research activities, the propagation and concentration of infectious pathogens requires the processing of large "production quantity" quantities of infectious pathogens.Large numbers of infectious pathogens may pose an increased risk, so it is not possible to limit "production quantities" to a limited volume or concentration for any given pathogen.Therefore, laboratory managers must evaluate the experimental operations to be performed and select operating techniques, diffusion-proof instruments, and facilities appropriate to the hazard, regardless of the volume and concentration of the pathogens involved.
Sometimes laboratory directors should choose a higher biosafety level than recommended.For example, the unique nature of the planned experiment may require a higher level of biosafety (such as an inhalation study, which may require special non-proliferation restrictions on the aerosols generated by the experiment); or the laboratory's proximity to areas requiring special considerations may also require a higher level of biosafety. biosafety levels (e.g. diagnostic laboratories located near patient care areas).Likewise, recommended biosecurity levels can be applied to compensate for deficiencies caused by the absence of certain recommended protective measures.For example, for microorganisms for which "Class" level is recommended, routine or repetitive operations (such as diagnostic procedures for the proliferation of a pathogen for the purpose of identification, typing, and sensitivity testing) are performed in a laboratory with facility characteristics that meet the "Class" level. , as long as the recommended standard microbiological operating procedures are strictly followed, and the special operating procedures and safety equipment suitable for the "level" level can also be achieved, an acceptable safety level can be achieved.
At the "level [-]" level, routine diagnostic work on clinical samples can be safely performed using "level [-] operating techniques and procedures."Further research work (including co-cultivation, viral replication studies, or operations involving concentrating viruses) may be performed in Class [-] facilities using Class [-] operating techniques and procedures.
related information
Among the pathogens of infectious diseases, some can complete life activities independently, while others cannot complete life activities independently.For example: the pathogens of AIDS, hand, foot and mouth disease, and polio cannot complete life activities independently; while the pathogens of tuberculosis can complete life activities independently.
Pathogen [Chinese word]
Pathogen [Chinese word]
Choosing an appropriate biosafety level for working with a specific pathogen or for animal studies depends on many factors, important among which are: virulence of the pathogen or toxin, pathogenicity, biological stability, route of transmission, and infectivity of the pathogen , the nature or functions of the laboratory, the operating procedures and methods involved in the pathogen, the local prevalence of the pathogen, the availability of effective vaccines and treatments.Provides guidance on selecting appropriate biosafety levels.It includes special information about laboratory hazards and recommended practical protective measures that can significantly reduce the risk of laboratory-associated infections.Includes pathogens that meet one or more of the following criteria: have been proven to be hazardous to laboratory personnel handling infectious substances (such as hepatitis B virus, Mycobacterium tuberculosis); have a high likelihood of causing laboratory-related infections, including no documented evidence Laboratory-related infections (such as exotic arboviruses); or the consequences of the infection are severe.
culture isolation
Although it is slower and more complicated than the direct inspection method, it is more accurate and has a wider application range and can be used for almost all pathogens.Generally, except for viruses, chlamydia and rickettsiae, non-living media can be used for culture and isolation.There are many types of culture media that can be selected according to different pathogens.After the pathogen is cultured and isolated, various tests can also be conducted, such as fermentation test, virulence test, etc., which are very important for the further identification of the pathogen.Viruses, chlamydia and rickettsia lack various enzymes necessary to maintain life. They cannot absorb nutrients from the culture medium like bacteria and use their own enzymes to synthesize the various components they need. They cannot use inanimate substances. Culture medium must be inoculated into a living organism, using the body's enzymes to synthesize the various components they require.This method is called "virus isolation", "chlamydia isolation" or "rickettsia isolation".
There are generally three methods of separation:
1 Tissue culture.The simplest and most commonly used;
2. Inoculation of animal embryos (such as chicken embryos and duck embryos);
3. Animal vaccination, such as inoculating mice, guinea pigs, etc.Different viruses, chlamydia or rickettsia often require different isolation methods. After positive isolation, various tests (such as serological tests, etc.) are often required to finally determine their type.Direct examination of pathogens is often performed simultaneously with culture isolation of the pathogens.
In addition to the above two methods, there are also some special inspection methods.For example, for people or animals suspected of being infected, the diagnosis can be confirmed by examining specific inclusion bodies (Negri bodies) in their brain tissue; to detect hepatitis B surface antigen, reverse passive hemagglutination (RPHA) enzyme-linked immunosorbent assay (ELISA) can be used ) and radioimmunoassay (RIA) and other methods; immunoelectron microscopy can be used to check the hepatitis A virus in stool.Molecular hybridization or nucleic acid analysis methods can also be used to detect pathogenic nucleic acids in the patient's blood, tissue or excrement to assist diagnosis. For example, hepatitis B virus nucleic acid in blood and liver tissue can be detected by molecular hybridization; feces Rotavirus can be detected using nucleic acid analysis methods.Since the various antigens of the pathogen and the nucleic acid of the pathogen are specific components of the pathogen, if they appear positive, it means that the pathogen is positive. Therefore, these methods also have great potential to confirm the diagnosis.
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non-cellular organisms
This entry was created by "anonymous user".
non-cellular organisms
Non-cellular organisms, or acellular life, are life that do not have cellular structures present for at least part of their life cycle.Historically, most (descriptive) definitions of life assumed that an organism must be composed of one or more cells, but this is no longer considered necessary, and modern standards allow for life forms based on other structural arrangements.
The leading candidates for non-cellular life are viruses.Some biologists consider viruses to be organisms, but others do not.Their main objection is that no known viruses can reproduce autonomously: they must rely on cells to replicate them.
Engineers sometimes use the term artificial life to refer to software and robots inspired by biological processes, but these do not meet any biological definition of life.
Viruses as non-cellular life
(millions of years ago) *Ice Age
For many years after its discovery as a pathogen, the nature of the virus remained unclear.They were first described as poisons or toxins and then as infectious proteins, but as microbiology progressed it became clear that they also possess genetic material, a defined structure, and the ability to assemble spontaneously from their component parts.This sparked widespread debate about whether they should be considered fundamentally organic or inorganic - as very small biological organisms or very large biochemical molecules - and since the 1950s many scientists have believed that viruses exist in chemistry and the boundaries of life; the gray area between living and non-living things.
Viral replication and self-assembly is of great significance to the study of the origin of life because it further supports the hypothesis that life may have begun with self-assembling organic molecules.
viroid
Viroids are the smallest infectious pathogens known to biologists, consisting only of short, circular, single-stranded RNA with no protein coat.They are mainly plant pathogens, some are animal pathogens, and some of them are of commercial importance.The size of viroid genomes is very small, ranging from 246 to 467 nucleobases.By comparison, the smallest known virus capable of causing infection on its own has a genome size of about 2,000 nucleobases.Viroids are the first known representatives of the new biological field of subviral pathogens.
Virus-like RNA does not encode any protein.Its replication machinery hijacks RNA polymerase II, a host cell enzyme normally associated with the synthesis of messenger RNA from DNA, and uses the virus-like RNA as a template to catalyze the rolling circle synthesis of new RNA.Some viroids are ribozymes with catalytic properties that allow self-cleavage and ligation of unit-sized genomes from larger replication intermediates.
Viroids have significance beyond plant virology because one possible explanation for their origin is that they represent living relics of a postulated ancient, non-cellular RNA world before the evolution of DNA or proteins.
non-cellular organisms
This idea was first proposed in the 80s and became popular again in the 2010s to explain key intermediate steps in the evolution of life from inanimate matter (natural occurrence).
Taxonomy
When discussing taxonomic realms of life, the terms Acytota and Aphanobionta are occasionally used as names for the viral kingdom, realm, or empire.The corresponding name for cellular life would be Cytota.Non-cellular organisms and cellular life will be the two top subdivisions of life, and life as a whole will be called organisms, Naturae, Biotae, or Vitae.The taxon Cytota will include its own three top-level subdivisions, Domain Bacteria, Domain Archaea, and Domain Eukarya.
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