A viral plaque is a visible structure formed after introducing a viral sample to a

cell culture Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas Burrows. This tec ...

grown on some

nutrient medium A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss ''Physcomitrella patens''. Different ...

. The

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsk ...

will replicate and spread, generating regions of cell destruction known as plaques. For example, Vero cell or other tissue cultures may be used to investigate an

influenza virus ''Orthomyxoviridae'' (from Greek ὀρθός, ''orthós'' 'straight' + μύξα, ''mýxa'' 'mucus') is a family of negative-sense RNA viruses. It includes seven genera: ''Alphainfluenzavirus'', ''Betainfluenzavirus'', '' Gammainfluenzavirus'', ' ...

coronavirus Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the co ...

, while various bacterial cultures would be used for

bacteriophages A bacteriophage (), also known informally as a ''phage'' (), is a duplodnaviria virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν ('), meaning "to devour". Bacterio ...

. Counting the number of plaques can be used as a method of

virus quantification Virus quantification involves counting the number of viruses in a specific volume to determine the virus concentration. It is used in both research and development (R&D) in commercial and academic laboratories as well as production situations whe ...

. These plaques can sometimes be detected visually using

colony counter In microbiology, colony-forming unit (CFU, cfu or Cfu) is a unit which estimates the number of microbial cells ( bacteria, fungi, viruses etc.) in a sample that are viable, able to multiply via binary fission under the controlled conditions. Coun ...

s, in much the same way as bacterial colonies are counted; however, they are not always visible to the naked eye, and sometimes can only be seen through a

microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisi ...

, or using techniques such as staining (e.g. neutral red for eukaryotes or giemsa for bacteria) or

immunofluorescence Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on microbiological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to spe ...

. Special computer systems have been designed with the ability to scan samples in batches. The appearance of the plaque depends on the host strain, virus and the conditions. Highly virulent or

lytic The lytic cycle ( ) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bacter ...

strains create plaques that look clear (due to total cell destruction), while strains that only kill a fraction of their hosts (due to partial resistance/lysogeny), or only reduce the rate of cell growth, give turbid plaques. Some partially lysogenic phages give bull's-eye plaques with spots or rings of growth in the middle of clear regions of complete lysis.

References

External links

* An image o
Bacteriophage plaques in agar
{{DEFAULTSORT:Viral Plaque Virology Bacteriophages

See also

References

External links