Common strategies for antigenic variation by bacterial. This video outlines the different ways that bacteria can generate genetic variation, especially in the light of the fact that meiosis is not a part of their. Phase and antigenic variation in bacteria clinical. What is the difference between antigenic and phase variation. While the antigenic variation is the modification of the.
When a bacterial cell divides, the two daughter cells are generally indistinguishable. The phase variation is the reversible ability of some bacteria to turn an and off the expression of genes coding for the surface antigens. Request pdf antigenic variation in bacterial pathogens antigenic variation is a strategy used by a broad diversity of microbial pathogens to persist within the mammalian host. Antigenic variation mechanisms that were first defined in these bacteria, including phase variation by slippedstrand mispairing during dna replication and gene conversion, have provided a. Phenotypic variation in bacteria has long been recognized and has been a focus of study mainly in bacterial pathogens. Boot biocentrum amsterdam, university of amsterdam, plantage muidergracht 12, 1018 tv amsterdam, the netherlands. The neisseria species vary their pili protein polymers made up of subunits called pilin which play a critical role in bacterial adhesion, and stimulate a. A longterm epigenetic memory switch controls bacterial. Variability in the expression of virulence genes is observed when the bacteria are exposed to activating conditions nielsen et al. This microbial phenotype heterogeneity is a nongenetic variation, i. Phase variation in bacteria was first identified in the expression of flagella in. In otype bacteria the expression of both the endogenote h1 the phase1 flagellar antigen gene and the exogenote h1 introduced by abortive transduction.
Changes in the antigenic molecules of an invasive organism exposed to the immune system over the course of an infection. Phase and antigenic variation result in a heterogenic phenotype of a clonal bacterial population, in which individual cells either express the phasevariable proteins or not, or express one of. This form of regulation has been identified mainly, but by no means exclusively, for a wide variety of surface structures in animal. Phase and antigenic variation result in a heterogenic phenotype of a clonal bacterial population, in which individual cells either express the phasevariable proteins or not, or express one of multiple antigenic forms of the protein, respectively. Horizontal gene transfer among bacteria and its role in. Antigenic variation in bacteria is best demonstrated by species of the genus neisseria most notably, neisseria meningitidis and neisseria gonorrhoeae, the gonococcus. Mechanisms that generate variation in prokaryote populations.
On solid medium, a clone is manifested as an easily isolated colony. Antigenic variation an overview sciencedirect topics. In an excellent chapter on antigenic variation in bacteria, barbour listed three criteria that must be ful. Antigenic variation is a process by which many infectious agents, including some pathogenic viruses, bacteria, fungi, and parasites, evade the defense responses of the vertebrate immune system. Phase and antigenic variation govern competition dynamics. This form of regulation has been identified mainly.
In contrast, antigenically variant bacteria have evolved mechanisms utilizing a stable genome that safeguards progeny fitness. Common strategies for antigenic variation by bacterial, fungal and. Expression, secretion and antigenic variation of bacterial s. Thus, a single bacterial cell can produce a large population of identical cells or clone. Antigenic variation in bacterial pathogens request pdf. Transduction, transformation, conjugation, transposable elements. Summary phase and antigenic variation result in a heterogenic phenotype of a clonal bacterial population, in which individual cells either express the phasevariable proteins or not, or express one of multiple antigenic forms of the protein, respectively. Phase and antigenic variation in bacteria request pdf. Phase and antigenic variation can serve several roles in bacteria, e. Studies on ho variants in salmonella in relation to phase variation. Antigenic variation is a strategy used by a broad diversity of microbial pathogens, from small rna viruses, notably the human immunodeficiency virus hiv, to large eukaryotic parasites with multiple chromosomes, illustrated by trypanosomal and malarial parasites, to persist within mammalian hosts 2,3. Expression, secretion and antigenic variation of bacterial.
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