Horizontal gene transfer (HGT) is a process where genetic material moves between organisms within the same generation, unlike vertical gene transfer, which occurs from parent to offspring. HGT plays a crucial role in microbial evolution, adaptation, and survival, particularly in shared environments like the human gut.
Mobile genetic elements such as plasmids, prophages, integrons, insertion sequences, and transposons facilitate this process. HGT occurs through three primary mechanisms: transformation, conjugation, and transduction.
In transformation, a recipient cell directly takes foreign DNA from its surroundings. Conjugation involves direct cell-to-cell contact, transferring DNA from a donor to a recipient, often via plasmids. Conversely, transduction is mediated by bacteriophages, viruses that infect bacteria, which transfer genetic material between bacterial cells.
Once foreign DNA enters the recipient cell, it may integrate into the host genome through recombination. This process involves the RecA protein, which assists in strand exchange, forming a recombinant hybrid genome with new genetic traits.
HGT significantly impacts microbial communities by transferring genes related to metabolism, virulence, and antibiotic resistance. For instance, pathogenicity islands—clusters of genes associated with toxin production and virulence—can transform harmless bacterial strains into pathogenic ones. In archaea, HGT helps repair UV-induced damage, allowing these microorganisms to adapt rapidly to extreme environments.
This genetic exchange supports microbial diversity and ecological adaptability, influencing beneficial and harmful microbial traits within various ecosystems.
Horizontal gene transfer, or HGT, moves genes between organisms of the same generation, unlike vertical gene transfer, which passes genes to offspring.
HGT is facilitated by mobile genetic elements such as plasmids, prophages, integrons, insertion sequences, and transposons.
Three mechanisms drive HGT. Transformationoccurs when a recipient cell directly takes foreign DNA from the surrounding environment.
In conjugation, cell-to-cell contact directly transfers DNA from host to recipient. In transduction, a bacteriophage mediates DNA transfer.
Upon uptake, foreign DNA is integrated through recombination, with RecA facilitating strand exchange, creating a recombinant hybrid.
Genes related to metabolism, virulence, or resistance commonly transfer through HGT in microbes within shared environments such as the human gut.
HGT contributes to the formation of pathogenicity islands – clusters of toxin, or virulence-related genes – that enhance pathogenicity in certain strains.
In some archaea, acquired DNA aids in UV damage repair, enabling rapid adaptation in extreme environments.
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