Horizontal gene transfer
Horizontal gene transfer (HGT) refers to the transfer of genetic material between organisms in ways other than traditional reproduction. It is a prevalent phenomenon among bacteria and viruses, but less common among multicellular organisms or between multicellular organisms and bacteria. HGT occurs through several mechanisms, including transduction (virus-mediated gene transfer), conjugation (direct transfer between touching cells), and transformation (uptake of environmental DNA). This genetic exchange can significantly impact bacterial populations by providing new traits, such as antibiotic resistance or the ability to exploit new resources.
While concerns have been raised about genetically modified organisms (GMOs) potentially transmitting their engineered genes to wild bacteria, research indicates that such transfers are limited and not well-documented in natural environments. Similarly, studies show that gene transfer from GM plants to bacteria or animals consuming them occurs at a very low rate. Additionally, HGT plays a role in various applications, including the fermentation of foods, where it may enhance quality but also raise concerns about the presence of antibiotic-resistant bacteria. Overall, HGT is a complex and influential factor in genetics, evolution, and ecology that warrants further exploration and understanding.
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Horizontal gene transfer
DEFINITION: Transfer of deoxyribonucleic acid between organisms by means other than reproduction
Horizontal gene transfer is widespread among bacteria and viruses but relatively rare between multicellular organisms or between multicellular organisms and bacteria. Environmentalists have expressed concerns that genetically engineered organisms could potentially pass their artificially introduced genes to other nonrelated organisms and thus change local and global ecologies, but research has shown that there are limits to the extent of such transfer.
Deoxyribonucleic acid (DNA) is used by all cell-based life on the earth to store genetic information. Parents pass their DNA to their offspring during reproduction. DNA transfer by means of reproduction is referred to as vertical gene transfer. DNA transfer between organisms that is not the result of reproduction is known as horizontal gene transfer (HGT) or lateral gene transfer.
Bacterial genomic studies have demonstrated that HGT is rather common between bacteria. HGT occurs by three different mechanisms: transduction, or DNA transfer between cells by viruses; conjugation, in which cells physically touch each other and transfer DNA; and transformation, or the direct uptake of DNA from the environment by cells. The rate of HGT between the common intestinal bacterium Escherichia coli and its close relative Salmonella is approximately one gene every 50,000 years, and 18 percent of the genome of E. coli was acquired through HGT. Genomic studies have also shown that not all genes are transferred at the same rate and not all groups of organisms experience HGT to the same extent.
HGT between bacteria can imbue bacterial species with new genes and opportunities to invade new environments. HGT can give bacteria antibiotic resistance, the ability to cause diseases, or the capacity to utilize new food sources. Genetically modified bacteria, which contain novel genes, can potentially move their new genes into large populations of bacteria. The introduction of new genetic material into bacteria has the potential to alter seriously the ecological and pathogenic character of bacterial species.
HGT from bacteria to multicellular organisms occurs at a lower rate. The plant pathogen Agrobacterium transfers DNA to plants by means of a conjugation-type mechanism. Likewise, intracellular parasites can also transfer genes into their multicellular plant or animal hosts. With respect to HGT from multicellular organisms to bacteria, genomic analyses have confirmed that bacteria have acquired genes from multicellular organisms. A consequence of these data is that genetically modified (GM) plants, which are commonly used in modern agriculture, might be able to transfer genes to soil bacteria. However, even though GM plants can transfer to soil bacteria under laboratory conditions, such transfer has not been definitively demonstrated under natural conditions in field studies. Studies have addressed the transfer of genes from GM plants to bacteria in the digestive tracts of those animals that consume foods made from GM plants, and the research has shown that such transfer is highly inefficient. Other studies on animals and humans have established that the transfer of genes from GM plants to animal species that consume GM foods does not occur at any significant rate. In the 2020s, researchers have been studying the role of HGT in fermented foods, such as dairy products and fermented fruits, vegetables, and meat products. They believe that HGT can improve the quality of fermented foods. However, concern exists about these foods harboring antibiotic resistance bacteria.
HGT to viruses from plants and animals is somewhat common. For example, viral infections of GM plants cause the production of novel plant viruses that have exchanged genes with the host plant. This generates new viruses with new genes and novel properties. Similarly, when animal viruses infect animal cells, they can acquire altered versions of animal genes that transform them into tumor-causing viruses.
Bibliography
Bushman, Frederic. Lateral DNA Transfer: Mechanisms and Consequences. Cold Spring Harbor: Cold Spring Harbor Laboratory P, 2002. Print.
Fedoroff, Nina V., and Nancy Marie Brown. Mendel in the Kitchen: A Scientist’s View of Genetically Modified Food. Washington, DC: Joseph Henry, 2006. Print.
Stewart, C. Neal, Jr. Genetically Modified Planet: Environmental Impacts of Genetically Engineered Plants. New York: Oxford UP, 2004. Print.
Wang, Ruhong, et al. "Recent Developments in HGT with the Adaptive Innovation of Fermented Foods." Critical Reviews in Food Science and Nutrition, vol. 63, no. 5, 1 June 2022, doi.org/10.1080/10408398.2022.2081127. Accessed 17 June 2024.