Inbiology, astrain is a genetic variant, a subtype ora culture within a biologicalspecies. Strains are often seen as inherently artificial concepts, characterized by a specific intent for genetic isolation.[1] This is most easily observed inmicrobiology where strains are derived from a single cellcolony and are typically quarantined by the physical constraints of aPetri dish. Strains are also commonly referred to withinvirology,botany, and withrodents used in experimental studies.[citation needed]
It has been said that "there is no universally accepted definition for the terms 'strain', 'variant', and 'isolate' in the virology community, and most virologists simply copy the usage of terms from others".[2]
A strain is agenetic variant or subtype of a microorganism such as abacterial strain or a specific strain of avirus, orfungus. For example, a "flu strain" is a certain biological form of theinfluenza or "flu" virus. These flu strains are characterized by their differing isoforms of surface proteins. New viral strains can be created due to mutation or swapping of genetic components when two or more viruses infect the same cell in nature.[3] These phenomena are known respectively asantigenic drift andantigenic shift. Microbial strains can also be differentiated by their genetic makeup using metagenomic methods to maximize resolution within species.[4] This has become a valuable tool to analyze themicrobiome.[citation needed]
Scientists have modified strains of viruses in order to study their behavior, as in the case of theH5N1 influenza virus. While funding for such research has aroused controversy at times due to safety concerns, leading to a temporary pause, it has subsequently proceeded.[5][6]
In biotechnology, microbial strains have been constructed to establish metabolic pathways suitable for treating a variety of applications.[7] Historically, a major effort of metabolic research has been devoted to the field of biofuel production.[8]Escherichia coli is most common species for prokaryotic strain engineering. Scientists have succeeded in establishing viable minimal genomes from which new strains can be developed.[9] These minimal strains provide a near guarantee that experiments on genes outside the minimal framework will not be effected by non-essential pathways. Optimized strains ofE. coli are typically used for this application.E. coli are also often used as a chassis for the expression of simple proteins. These strains, such as BL21, are genetically modified to minimize protease activity, hence enabling potential for high efficiency industrial scaleprotein production.[10]
Strains ofyeasts are the most common subjects of eukaryotic genetic modification, especially with respect toindustrial fermentation.[11]
The term has no official ranking status in botany; the term refers to the collective descendants produced from a common ancestor that share a uniform morphological or physiological character.[12] A strain is a designated group of offspring that are either descended from a modified plant (produced by conventional breeding or by biotechnological means), or which result from genetic mutation.[citation needed]
As an example, somerice strains are made by inserting newgenetic material into a rice plant,[13] all thedescendants of the genetically modified rice plant are a strain with uniquegenetic information that is passed on to later generations; the strain designation, which is normally a number or a formal name, covers all the plants that descend from the originally modified plant. The rice plants in the strain can be bred to other rice strains orcultivars, and if desirable plants are produced, these are further bred to stabilize the desirable traits; the stabilized plants that can be propagated and "come true" (remain identical to the parent plant) are given acultivar name and released into production to be used by farmers.[citation needed]
Alaboratory mouse orrat strain is a group of animals that isgenetically uniform. Strains are used in laboratory experiments. Mouse strains can beinbred,mutated, orgenetically modified, while rat strains are usuallyinbred. A given inbred rodent population is considered genetically identical after 20 generations of sibling-mating. Many rodent strains have been developed for a variety of disease models, and they are also often used to test drug toxicity.[14][15][16]
Thecommon fruit fly (Drosophila melanogaster) was among the first organisms used forgenetic analysis, has a simplegenome, and is very well understood. It has remained a popular model organism for many other reasons, like the ease of its breeding and maintenance, and the speed and volume of its reproduction. Various specific strains have been developed, including a flightless version with stunted wings (also used in the pet trade aslive food for small reptiles and amphibians).[citation needed]
