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Horizontal gene transfer (HGT) refers to the transfer of
There is evidence for historical horizontal transfer of the following genes:
In a May 2010 article in Nature, Douglas Theobald[64] argued that there was indeed one Last Universal Common Ancestor to all existing life and that horizontal gene transfer has not destroyed our ability to infer this.
With regard to how horizontal gene transfer affects evolutionary theory (common descent, universal phylogenetic tree) Carl Woese says:
The article continues with:
Again on p. 76, the article continues with:
[62] by W. Uprooting the Tree of Life
Using single genes as [61]
Biologist Johann Peter Gogarten suggests "the original metaphor of a tree no longer fits the data from recent genome research" therefore "biologists should use the metaphor of a mosaic to describe the different histories combined in individual genomes and use the metaphor of a net to visualize the rich exchange and cooperative effects of HGT among microbes."[24] There exist several methods to infer such phylogenetic networks.
For example, the most common gene to be used for constructing phylogenetic relationships in prokaryotes is the 16s rRNA gene since its sequences tend to be conserved among members with close phylogenetic distances, but variable enough that differences can be measured. However, in recent years it has also been argued that 16s rRNA genes can also be horizontally transferred. Although this may be infrequent the validity of 16s rRNA-constructed phylogenetic trees must be reevaluated.[60]
Horizontal gene transfer is a potential confounding factor in inferring phylogenetic trees based on the sequence of one gene.[59] For example, given two distantly related bacteria that have exchanged a gene a phylogenetic tree including those species will show them to be closely related because that gene is the same even though most other genes are dissimilar. For this reason it is often ideal to use other information to infer robust phylogenies such as the presence or absence of genes or, more commonly, to include as wide a range of genes for phylogenetic analysis as possible.
Genetic engineering is essentially horizontal gene transfer, albeit with synthetic expression cassettes. The Sleeping Beauty transposon system[55] (SB) was developed as a synthetic gene transfer agent that was based on the known abilities of Tc1/mariner transposons to invade genomes of extremely diverse species.[56] The SB system has been used to introduce genetic sequences into a wide variety of animal genomes.[57][58]
Update: Genome Biol. 2015 Mar 13;16(1):50. doi: 10.1186/s13059-015-0607-3. Expression of multiple horizontally acquired genes is a hallmark of both vertebrate and invertebrate genomes. Crisp A, Boschetti C, Perry M, Tunnacliffe A, Micklem G. http://www.ncbi.nlm.nih.gov/pubmed/25785303
"Sequence comparisons suggest recent horizontal transfer of many genes among diverse species including across the boundaries of phylogenetic 'domains'. Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes".[37]
Horizontal gene transfer is common among bacteria, even among very distantly related ones. This process is thought to be a significant cause of increased drug resistance[1][33] when one bacterial cell acquires resistance, and the resistance genes are transferred to other species.[34][35] Transposition and horizontal gene transfer, along with strong natural selective forces have led to multi-drug resistant strains of S. aureus and many other pathogenic bacteria.[27] Horizontal gene transfer also plays a role in the spread of virulence factors, such as exotoxins and exoenzymes, amongst bacteria.[1] A prime example concerning the spread of exotoxins is the adaptive evolution of Shiga toxins in E. coli through horizontal gene transfer via transduction with Shigella species of bacteria.[36] Strategies to combat certain bacterial infections by targeting these specific virulence factors and mobile genetic elements have been proposed.[7] For example, horizontally transferred genetic elements play important roles in the virulence of E. coli, Salmonella, Streptococcus and Clostridium perfringens.[1]
The virus called Mimivirus infects amoebae. Another virus, called Sputnik, also infects amoebae, but it cannot reproduce unless mimivirus has already infected the same cell.[30] "Sputnik’s genome reveals further insight into its biology. Although 13 of its genes show little similarity to any other known genes, three are closely related to mimivirus and mamavirus genes, perhaps cannibalized by the tiny virus as it packaged up particles sometime in its history. This suggests that the satellite virus could perform horizontal gene transfer between viruses, paralleling the way that bacteriophages ferry genes between bacteria.".[31] Horizontal transfer is also seen between geminiviruses and tobacco plants.[32]
Horizontal gene transfer is typically inferred using bioinformatic methods, either by identifying atypical sequence signatures ("parametric" methods) or by identifying strong discrepancies between the evolutionary history of particular sequences compared to that of their hosts.
A transposon (jumping gene) is a mobile segment of DNA that can sometimes pick up a resistance gene and insert it into a plasmid or chromosome, thereby inducing horizontal gene transfer of antibiotic resistance.[27]
There are several mechanisms for horizontal gene transfer:[1][25][26]
Some have argued that the process may be a hidden hazard of genetic engineering as it could allow transgenic DNA to spread from species to species.[21]
Due to the increasing amount of evidence suggesting the importance of these phenomena for evolution (see below) molecular biologists such as Peter Gogarten have described horizontal gene transfer as "A New Paradigm for Biology".[24]
Richardson and Palmer (2007) state: "Horizontal gene transfer (HGT) has played a major role in bacterial evolution and is fairly common in certain unicellular eukaryotes. However, the prevalence and importance of HGT in the evolution of multicellular eukaryotes remain unclear."[23]
There is some evidence that even higher plants and animals have been affected and this has raised concerns for safety.[21] It has been suggested that lateral gene transfer to humans from bacteria may play a role in cancer.[22]
As Jain, Rivera and Lake (1999) put it: "Increasingly, studies of genes and genomes are indicating that considerable horizontal transfer has occurred between prokaryotes"[18] (see also Lake and Rivera, 2007).[19] The phenomenon appears to have had some significance for unicellular eukaryotes as well. As Bapteste et al. (2005) observe, "additional evidence suggests that gene transfer might also be an important evolutionary mechanism in protist evolution."[20]
Horizontal gene transfer was first described in Seattle in 1951 in a publication which demonstrated that the transfer of a viral gene into Corynebacterium diphtheriae created a virulent from a non-virulent strain,[12] also simultaneously solving the riddle of diphtheria (that patients could be infected with the bacteria but not have any symptoms, and then suddenly convert later or never),[13] and giving the first example for the relevance of the lysogenic cycle.[14] Inter-bacterial gene transfer was first described in Japan in a 1959 publication that demonstrated the transfer of antibiotic resistance between different species of bacteria.[15][16] In the mid-1980s, Syvanen[17] predicted that lateral gene transfer existed, had biological significance, and was involved in shaping evolutionary history from the beginning of life on Earth.
Artificial horizontal gene transfer is a form of genetic engineering.
[11][10] Most thinking in
Horizontal gene transfer is the primary reason for bacterial antibiotic resistance,[1][2][3][4][5] and plays an important role in the evolution of bacteria that can degrade novel compounds such as human-created pesticides[6] and in the evolution, maintenance, and transmission of virulence.[7] This horizontal gene transfer often involves temperate bacteriophages and plasmids.[8][9] Genes that are responsible for antibiotic resistance in one species of bacteria can be transferred to another species of bacteria through various mechanisms (e.g., via F-pilus), subsequently arming the antibiotic resistant genes' recipient against antibiotics, which is becoming a medical challenge to deal with.
[1]
Biology, Biotechnology, Genetics, Dna, Genetically modified food
Evolution, Biology, Mutation, Epigenetics, Ecology
Nobel Prize in Physiology or Medicine, Dna, Genome, Transposon, Retrotransposons
Amoebozoa, Bacteria, Rhizaria, Animal, Fungus
Molecular biology, Chromosome, Genetic engineering, Literature, Bacteria
Phosphorus, Genetic engineering, Synthetic biology, Diabetes, Algae
Bacteria, Gene, Genetics, Chromosome, Genetic engineering
Verbena, Species, United States Department of Agriculture, Evolution, Verbenaceae