Abstract
Integrons are considered hot spots for bacterial evolution, since these platforms allow one-step genomic innovation by capturing and expressing genes that provide advantageous novelties, such as antibiotic resistance. The acquisition and shuffling of gene cassettes featured by integrons enable the population to rapidly respond to changing selective pressures. However, in order to avoid deleterious effects and fitness burden, the integron activity must be tightly controlled, which happens in an elegant and elaborate fashion, as discussed in detail in the present review. Here, we aimed to provide an up-to-date overview of the complex regulatory networks that permeate the expression and functionality of integrons at both transcriptional and translational levels. It was possible to compile strong shreds of evidence clearly proving that these versatile platforms include functions other than acquiring and expressing gene cassettes. The well-balanced mechanism of integron expression is intricately related with environmental signals, host cell physiology, fitness, and survival, ultimately leading to adaptation on the demand.
Highlights
IntroductionIntegrons are versatile genetic platforms involved with the acquisition, stockpiling, excision, and rearrangements of gene cassettes by site-specific recombination events mediated by integrase activity [1]
Integron Functionality Is Directly Linked with Adaptation on DemandIntegrons are versatile genetic platforms involved with the acquisition, stockpiling, excision, and rearrangements of gene cassettes by site-specific recombination events mediated by integrase activity [1]
This review aimed to provide an up-to-date overview of the fine-tuning regulation of integrase and gene cassette expression at both transcriptional and translational levels, and of the intricate relationship between integrons and cell physiology components that feature these platforms as powerful tools for genome innovation and bacterial adaptation
Summary
Integrons are versatile genetic platforms involved with the acquisition, stockpiling, excision, and rearrangements of gene cassettes by site-specific recombination events mediated by integrase activity [1]. Together with its 50 conserved segment (CS), composed by the intI1 integrase gene, the attI1 recombination site, and the Pc and PintI1 promoters [2,3], the class 1 integrons present a 30 CS This region comprises the gene cassettes qacE∆1, fused in its 30 end with the sul, which confer resistance to quaternary ammonium compounds and sulfonamides, respectively, followed by orf of unknown function [1]. Fonseca and Vicente [11] observed that several other qnrVC alleles found in mobile platforms were always linked to CI-borne recombination sites from different Vibrio species This evidence strongly indicated that qnrVC was an archeological trait of CIs in the current MIs, corroborating the previous hypothesis that chromosomal integrons are the source of cassettes present in drug-resistance integrons [9]. This review aimed to provide an up-to-date overview of the fine-tuning regulation of integrase and gene cassette expression at both transcriptional and translational levels, and of the intricate relationship between integrons and cell physiology components that feature these platforms as powerful tools for genome innovation and bacterial adaptation
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