Centre National de la Recherche Scientifique, LMGM-UMR5100, Toulouse, France; Université de Toulouse, UPS, Laboratoire de Microbiologie et Génétique Moléculaires, Toulouse, France.
Trends Microbiol. 2013 Oct;21(10):516-21. doi: 10.1016/j.tim.2013.08.002. Epub 2013 Sep 8.
Bacteria are constantly challenged by foreign genetic elements such as bacteriophages and plasmids. Several defense systems provide immunity against such attackers, including restriction-modification (R-M) systems and clustered, regularly interspaced short palindromic repeats (CRISPRs). These systems target attacking DNA and thus antagonize natural transformation, which relies on uptake of exogenous DNA to promote acquisition of new genetic traits. It is unclear how this antagonization occurs, because transforming DNA is single stranded, and thus resistant to these immune systems. Here, we propose a simple model whereby these systems limit transformation by attack of transformed chromosomes once double strandedness is restored by chromosomal replication.
细菌经常受到噬菌体和质粒等外来遗传元件的挑战。几种防御系统为其提供了针对此类攻击的免疫力，包括限制修饰（R-M）系统和成簇、规律间隔的短回文重复序列（CRISPRs）。这些系统靶向攻击 DNA，从而拮抗自然转化，后者依赖于摄取外源 DNA 来促进获得新的遗传特征。目前尚不清楚这种拮抗作用是如何发生的，因为转化 DNA 是单链的，因此能够抵抗这些免疫系统。在这里，我们提出了一个简单的模型，即这些系统通过染色体复制恢复双链性后，攻击转化染色体来限制转化。
