horizontal gene transfer

Examples of horizontal gene transfer in the following topics:

• Horizontal Gene Transfer

  • Horizontal gene transfer (HGT) is the passing of genetic material between species by mechanisms other than from parent to offspring.
  • Horizontal gene transfer (HGT) is the introduction of genetic material from one species to another species by mechanisms other than the vertical transmission from parent(s) to offspring.
  • Horizontal gene transfer is the introduction of genetic material from one species to another species by mechanisms other than the vertical transmission from parent(s) to offspring.
  • Examples of mechanisms of horizontal gene transfer are listed for both prokaryotic and eukaryotic organisms.
  • Explain how horizontal gene transfer can make resolution of phylogenies difficult

• Pathogenicity Islands and Virulence Factors

  • Pathogenicity islands (PAIs) are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer.
  • Pathogenicity islands (PAIs) are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer.
  • Cryptic mobility genes may also be present, indicating the provenance as transduction.
  • PAIs are transferred through horizontal gene transfer events such as transfer by a plasmid, phage, or conjugative transposon.
  • They may be located on a bacterial chromosome or may be transferred within a plasmid.

• Pathogenicity Islands

  • Pathogenicity islands (PAIs) are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer.
  • Cryptic mobility genes may also be present, indicating the provenance as transduction.
  • They are transferred through horizontal gene transfer events such as transfer by a plasmid, phage, or conjugative transposon .
  • They may be located on a bacterial chromosome or may be transferred within a plasmid.
  • Pathogenicity islands are transferred horizontally, this details some of the ways that occurs.

• Plasmids and Lysogeny

  • In addition, plasmid DNA provides a mechanism by which horizontal gene transfer can occur, contributing to antibiotic resistance.
  • Horizontal gene transfer is a major mechanism promoting bacterial antibiotic resistance, as the plasmid DNA can transfer genes from one species of bacteria to another.
  • The plasmid DNA which is transferred often has developed genes that encode for resistance against antibiotics.
  • The process of horizontal gene transfer can occur via three mechanisms: transformation, transduction and conjugation.
  • There are three mechanisms by which horizontal gene transfer can occur.

• Gene Transfer in Archaea

  • This phenomenon is described as horizontal gene transfer.
  • Horizontal gene transfer (HGT) refers to the transfer of genes between organisms in a manner other than traditional reproduction.
  • Also termed lateral gene transfer, it contrasts with vertical transfer, the transmission of genes from the parental generation to offspring via sexual or asexual reproduction.
  • Archaea show high levels of horizontal gene transfer between lineages.
  • Taken together it is clear that gene transfer happens in Archaea, and probably is similar to horizontal gene transfer seen in the other domains of life.

• Genomic Similiarities between Distant Species

  • In addition, the mechanisms by which genomic similarities between distant species occur can include horizontal gene transfer.
  • Horizontal gene transfer (HGT), also known as lateral gene transfer, is the transfer of genes between unrelated species.
  • These gene transfers between species are the major mechanism whereby bacteria acquire resistance to antibiotics.
  • Although it is easy to see how prokaryotes exchange genetic material by HGT, it was initially thought that this process was absent in eukaryotes, followed by the idea that the gene transfers between multicellular eukaryotes should be more difficult.
  • According to DNA analysis, this ability is due to the transfer of fungal genes into the insect by HGT, presumably as the insect consumed fungi for food .

• Introduction to Plasmids

  • Plasmids can be considered part of the mobilome because they are often associated with conjugation, a mechanism of horizontal gene transfer.
  • Unlike viruses, they are naked DNA and do not encode genes necessary to encase the genetic material for transfer to a new host, though some classes of plasmids encode the sex pilus necessary for their own transfer.
  • Plasmid host-to-host transfer requires direct mechanical transfer by conjugation, or changes in incipient host gene expression allowing the intentional uptake of the genetic element by transformation.
  • Rather, plasmids provide a mechanism for horizontal gene transfer within a population of microbes and typically provide a selective advantage under a given environmental state.
  • Plasmids may carry genes that provide resistance to naturally occurring antibiotics in a competitive environmental niche, or the proteins produced may act as toxins under similar circumstances.

• Web, Network, and Ring of Life Models

  • The recognition of the importance of Horizontal gene transfer (HGT), especially in the evolution of prokaryotes, has caused some to propose abandoning the classic "tree of life" model.
  • The hypothesis is that eukaryotes evolved not from a single prokaryotic ancestor, but from a pool of many species that were sharing genes by HGT mechanisms.
  • Some individual prokaryotes were responsible for transferring the bacteria that caused mitochondrial development in the new eukaryotes, whereas other species transferred the bacteria that gave rise to chloroplasts.
  • Using the conditioned reconstruction algorithm, it proposes a ring-like model in which species of all three domains (Archaea, Bacteria, and Eukarya) evolved from a single pool of gene-swapping prokaryotes.
  • Ford Doolittle, the "tree of life" arose from a community of ancestral cells, has multiple trunks, and has connections between branches where horizontal gene transfer has occurred.

• Agrobacterium and Crown Gall Disease

  • Argobacterium causes Crown Gall Disease by transferring a DNA plasmid to the host plant, causing the host to make nutrients for it.
  • A. tumefaciens can transfer part of its DNA to the host plant, through a plasmid - a bacterial DNA molecule that is independent of a chromosome.
  • Bacteria normally use plasmids for horizontal gene transfer, so they can share genes with related bacteria to help them cope with stressful environments.
  • The new plasmid genes are expressed by the plant cells, and cause them to secrete enzymes that produce the amino acids octopine or nopaline.
  • It also carries genes for the biosynthesis of the plant hormones, auxin and cytokinins, and for the biosynthesis of opines, providing a carbon and nitrogen source for the bacteria.

• Limitations to the Classic Model of Phylogenetic Trees

  • The concept of genes being transferred between unrelated species was not considered as a possibility until relatively recently.
  • Horizontal gene transfer (HGT), also known as lateral gene transfer, is the transfer of genes between unrelated species.
  • Genes have been shown to be passed between species which are only distantly related using standard phylogeny, thus adding a layer of complexity to the understanding of phylogenetic relationships.
  • Finally, as an example of the ultimate gene transfer, theories of genome fusion between symbiotic or endosymbiotic organisms have been proposed to explain an event of great importance: the evolution of the first eukaryotic cell, without which humans could not have come into existence.