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In 1915, British bacteriologist Frederick Twort, superintendent of the Brown Institution of London, discovered a small agent that infected and killed bacteria. He believed the agent must be one of the following: a stage in the life cycle of the bacteria; an enzyme produced by the bacteria themselves, or; a virus that grew on and destroyed the ...
Filamentous bacteriophages are a family of viruses (Inoviridae) that infect bacteria, or bacteriophages.They are named for their filamentous shape, a worm-like chain (long, thin, and flexible, reminiscent of a length of cooked spaghetti), about 6 nm in diameter and about 1000-2000 nm long.
The virus has complex structural symmetry, with a capsid of the phage that is icosahedral (twenty faces) with an inner diameter of 55 nm and a tail 19 nm in diameter and 28.5 nm long attached to the capsid. [9] The ejection of proteins from the capsid upon infection causes the virus to change structure when it enters the cell. [10]
HIV is one of several viruses transmitted through sexual contact and by exposure to infected blood. The variety of host cells that a virus can infect is called its host range: this is narrow for viruses specialized to infect only a few species, or broad for viruses capable of infecting many. [13]: 123–124
Mimivirus shows many characteristics which place it at the boundary between living and non-living. It is as large as several bacterial species, such as Rickettsia conorii and Tropheryma whipplei , possesses a genomic size comparable to that of several bacteria, including those above, and codes for products previously not thought to be encoded ...
Life-cycle of a typical virus (left to right); following infection of a cell by a single virus, hundreds of offspring are released. When a virus infects a cell, the virus forces it to make thousands more viruses. It does this by making the cell copy the virus's DNA or RNA, making viral proteins, which all assemble to form new virus particles. [37]
There are more than 200 different types of viruses that can cause a common cold, which is usually just a mild infection in the upper respiratory tract, hence the feeling of a sore throat, runny ...
The virus then releases its genetic material (either single- or double-stranded RNA or DNA) into the cell. In some viruses this genetic material is circular and mimics a bacterial plasmid. At this stage the cell becomes infected and can also be targeted by the immune system. It is mostly aided by receptors on the surface of the cell.