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¶ … integrons has been driven by the alarmingly rapid appearance of antibiotic resistance among a number of bacteria liked to widespread disease in the last century. These bacteria have become an increasing threat to human health, and have often been featured in the media as "super bugs" that may evade any attempts to control their effects using antibiotic treatments. As a result, research into the genetic mechanisms that these drugs use to acquire genetic resistance has been followed with growing interest. The discovery of integrons may well therefore become known as one of the most important stepping-stones in this research (Rowe-Magnus).
Integrons are simply bacterial systems that allow the bacteria to capture and express DNA from other bacteria. Integrons capture foreign gene cassettes that code for important metabolic functions. Many of these gene cassettes contain genetic material that confers resistance to antibiotic drugs. There are over 70 different antibiotic resistance genes known in gene cassettes, a number that coincides with most of the antimicrobial drugs in use today (Rowe-Magnus).
Integrons are "natural cloning and expression systems that incorporate open reading frames and convert them to functional genes" (Rowe-Magnus et al., 652). An integrase is coded for by the integron platform, and then the integrase acts to mediate the recombination that occurs between a secondary target (attC site), and a primary recombination site (attI) (Rowe Magnus...
Clinically isolated bacteria that have resistance to multiple drugs, and have been shown to have integrons with up to eight resistance cassettes (Rowe-Magnus).
Integrons have likely played both an important and crucial role in the evolution of the bacterial kingdom, acting to an extent even beyond the recent acquisition of antibacterial resistance. A given bacterial genome can contain up to one fifth of its genome as foreign DNA (Rowe-Magnus et al.).
Multiresistant integrons (MRIs) have an extensive system of multiple combinations of antibiotic resistance gene cassettes. These elements are crucial to the rapid appearance of antibiotic resistance among a wide number of Gram-negative bacteria (Rowe-Magnus et al., 2001).
Despite their clear importance to the rapid appearance of antibiotic resistant bacteria, little was fully understood about the evolutionary history of MRIs (Rowe-Magnus). In a 2001 PNAS paper entitled "The evolutionary history of chromosomal super-integrons provides an ancestry for multiresistant integrons," Rowe-Magnus et al. investigated the evolutionary history of integrons.
The authors based their work on the recent discovery of a chromosomal integron in the Vibrio cholerae genome that was demonstrated to harbor hundreds of cassettes. They argue…
Works Cited
Rowe-Magnus, Dean. Faculty Research Focus, Laboratory Medicine and Pathobiology - Faculty
of Medicine, University of Toronto. 13 February 2004.
http://icarus.med.utoronto.ca/patho/faculty.asp?FacultyID=208
Rowe-Magnus, Dean A., Guerout, Anne-Marie, Ploncard, Pascaline, Dychino, Broderick,
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