Could DNA uptake be a side effect of bacterial adhesion and twitching motility?
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Could DNA uptake be a side effect of bacterial adhesion and twitching motility? M. Bakkali
Received: 4 October 2012 / Revised: 11 January 2013 / Accepted: 12 January 2013 / Published online: 5 February 2013 Ó The Author(s) 2013. This article is published with open access at Springerlink.com
Abstract DNA acquisition promotes the spread of resistance to antibiotics and virulence among bacteria. It is also linked to several natural phenomena including recombination, genome dynamics, adaptation and speciation. Horizontal DNA transfer between bacteria occurs via conjugation, transduction or competence for natural transformation by DNA uptake. Among these, competence is the only mechanism of transformation initiated and entirely controlled by the chromosome of the recipient bacteria. While the molecular mechanisms allowing the uptake of extracellular DNA are increasingly characterized, the function of competence for natural transformation by DNA uptake, the selective advantage maintaining it and the reasons why bacteria take up DNA in the first place are still debated. In this synthesis, I review some of the literature and discuss the four hypotheses on how and why do bacteria take up DNA. I argue that DNA uptake by bacteria is an accidental by-product of bacterial adhesion and twitching motility. Adhesion and motility are generally increased in stressful conditions, which may explain why bacteria increase DNA uptake in these conditions. In addition to its fundamental scientific relevance, the new hypothesis suggested here has significant clinical implications and finds further support from the fact that antibiotics sometimes fail to eliminate the targeted bacterium while inevitably causing stress to others. The widespread misuse of antibiotics may thus not only be selecting for resistant strains, but may also be causing bacteria to take up more
Communicated by Djamel Drider. M. Bakkali (&) Departamento de Gene´tica, Facultad de Ciencias, Universidad de Granada, Fuentenueva S/N, 18071 Granada, Spain e-mail: [email protected]
DNA with the consequent increase in the chances of acquiring drug resistance and virulence—a scenario in full concordance with the previously reported induction of competence genes by antibiotics in Streptococcus pneumoniae and Legionella pneumophila. Keywords Competence DNA uptake Transformation Horizontal gene transfer Type IV pilus Twitching motility Social gliding Swarming Bacteria
Acquisition of new genetic material by bacteria occurs by transduction, conjugation or competence for natural transformation by uptake of extracellular DNA (hereafter referred to simply as competence). These mechanisms of horizontal gene transfer (HGT) are sources of genetic diversity in the otherwise mostly clonal world of bacteria and can even interfere with speciation by blurring species boundaries [see (Fraser et al. 2007)]. HGT is central to the spread of virulence and resistance to antibiotics among human and livestock pathogens (Vazquez et al. 2001; Courvalin 2005; Sabia e
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