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Horizontal gene transfer is the primary mechanism for the spread of antibiotic resistance in bacteria, [8] [5] [9] [10] and plays an important role in the evolution of bacteria that can degrade novel compounds such as human-created pesticides [11] and in the evolution, maintenance, and transmission of virulence. [12]
This lateral gene transfer occurred also beyond the Darwinian threshold, after heredity or vertical gene transfer was established. [4] [5] "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 ...
Pathogenicity islands (PAIs), as termed in 1990, are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer. [1] [2] Pathogenicity islands are found in both animal and plant pathogens. [2] Additionally, PAIs are found in both gram-positive and gram-negative bacteria. [2]
Horizontal gene transfer was first observed in 1928, in Frederick Griffith's experiment: showing that virulence was able to pass from virulent to non-virulent strains of Streptococcus pneumoniae, Griffith demonstrated that genetic information can be horizontally transferred between bacteria via a mechanism known as transformation. [2]
An example is the viral transfer of DNA from one bacterium to another and hence an example of horizontal gene transfer. [2] [3] [page needed] Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA (which occurs in conjugation), and it is DNase resistant (transformation is susceptible to ...
It is a mechanism of horizontal gene transfer as are transformation and transduction although these two other mechanisms do not involve cell-to-cell contact. [ 4 ] Classical E. coli bacterial conjugation is often regarded as the bacterial equivalent of sexual reproduction or mating , since it involves the exchange of genetic material.
For example, a GI associated with pathogenesis is often called a pathogenicity island (PAIs), while GIs that contain many antibiotic resistant genes are referred to as antibiotic resistance islands. The same GI can occur in distantly related species as a result of various types of horizontal gene transfer (transformation, conjugation ...
Along with chromosomal DNA, most bacteria also contain small independent pieces of DNA called plasmids that often encode advantageous traits but are not essential to their bacterial host. Plasmids can be easily gained or lost by a bacterium and can be transferred between bacteria as a form of horizontal gene transfer.