Meijer Wilfried J J, Boer D Roeland, Ares Saúl, Alfonso Carlos, Rojo Fernando, Luque-Ortega Juan R, Wu Ling Juan
Laboratory 402, Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma, Canto Blanco, Madrid, Spain.
ALBA Synchrotron Light Source, Barcelona, Spain.
Front Mol Biosci. 2021 Mar 18;8:648468. doi: 10.3389/fmolb.2021.648468. eCollection 2021.
Bacterial conjugation is the main horizontal gene transfer route responsible for the spread of antibiotic resistance, virulence and toxin genes. During conjugation, DNA is transferred from a donor to a recipient cell via a sophisticated channel connecting the two cells. Conjugation not only affects many different aspects of the plasmid and the host, ranging from the properties of the membrane and the cell surface of the donor, to other developmental processes such as competence, it probably also poses a burden on the donor cell due to the expression of the large number of genes involved in the conjugation process. Therefore, expression of the conjugation genes must be strictly controlled. Over the past decade, the regulation of the conjugation genes present on the conjugative plasmid pLS20 has been studied using a variety of methods including genetic, biochemical, biophysical and structural approaches. This review focuses on the interplay between Rco, Rap and Phr*, the proteins that control the activity of the main conjugation promoter P located upstream of the conjugation operon. Proper expression of the conjugation genes requires the following two fundamental elements. First, conjugation is repressed by default and an intercellular quorum-signaling system is used to sense conditions favorable for conjugation. Second, different layers of regulation act together to repress the P promoter in a strict manner but allowing rapid activation. During conjugation, ssDNA is exported from the cell by a membrane-embedded DNA translocation machine. Another membrane-embedded DNA translocation machine imports ssDNA in competent cells. Evidences are reviewed indicating that conjugation and competence are probably mutually exclusive processes. Some of the questions that remain unanswered are discussed.
细菌接合是导致抗生素抗性、毒力和毒素基因传播的主要水平基因转移途径。在接合过程中，DNA通过连接两个细胞的复杂通道从供体细胞转移到受体细胞。接合不仅影响质粒和宿主的许多不同方面，从供体细胞的膜和细胞表面特性到其他发育过程如感受态，由于参与接合过程的大量基因的表达，它可能也给供体细胞带来负担。因此，接合基因的表达必须受到严格控制。在过去十年中，使用包括遗传学、生物化学、生物物理学和结构方法在内的多种方法研究了接合质粒pLS20上存在的接合基因的调控。本综述重点关注Rco、Rap和Phr*之间的相互作用，这些蛋白质控制着位于接合操纵子上游的主要接合启动子P的活性。接合基因的正确表达需要以下两个基本要素。首先，接合默认情况下受到抑制，细胞间群体感应系统用于感知有利于接合的条件。其次，不同层次的调控共同作用，以严格的方式抑制P启动子，但允许快速激活。在接合过程中，单链DNA通过膜嵌入的DNA转运机器从细胞中输出。另一种膜嵌入的DNA转运机器在感受态细胞中导入单链DNA。本文综述了表明接合和感受态可能是相互排斥过程的证据。还讨论了一些尚未得到解答的问题。
