Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-Consejo Superior de Investigaciones Científicas, Santander, Spain.
Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain.
Microbiol Mol Biol Rev. 2022 Mar 16;86(1):e0022220. doi: 10.1128/MMBR.00222-20. Epub 2021 Dec 8.
Plasmids are self-replicative DNA elements that are transferred between bacteria. Plasmids encode not only antibiotic resistance genes but also adaptive genes that allow their hosts to colonize new niches. Plasmid transfer is achieved by conjugation (or mobilization), phage-mediated transduction, and natural transformation. Thousands of plasmids use the rolling-circle mechanism for their propagation (RCR plasmids). They are ubiquitous, have a high copy number, exhibit a broad host range, and often can be mobilized among bacterial species. Based upon the replicon, RCR plasmids have been grouped into several families, the best known of them being pC194 and pUB110 (Rep_1 family), pMV158 and pE194 (Rep_2 family), and pT181 and pC221 (Rep_trans family). Genetic traits of RCR plasmids are analyzed concerning (i) replication mediated by a DNA-relaxing initiator protein and its interactions with the cognate DNA origin, (ii) lagging-strand origins of replication, (iii) antibiotic resistance genes, (iv) mobilization functions, (v) replication control, performed by proteins and/or antisense RNAs, and (vi) the participating host-encoded functions. The mobilization functions include a relaxase initiator of transfer (Mob), an origin of transfer, and one or two small auxiliary proteins. There is a family of relaxases, the MOB family represented by plasmid pMV158, which has been revisited and updated. Family secrets, like a putative open reading frame of unknown function, are reported. We conclude that basic research on RCR plasmids is of importance, and our perspectives contemplate the concept of One Earth because we should incorporate bacteria into our daily life by diminishing their virulence and, at the same time, respecting their genetic diversity.
质粒是自我复制的 DNA 元件，可以在细菌之间转移。质粒不仅编码抗生素抗性基因，还编码使宿主能够定植新生态位的适应性基因。质粒的转移是通过接合（或动员）、噬菌体介导的转导和自然转化来实现的。数千种质粒使用滚环机制进行繁殖（RCR 质粒）。它们无处不在，具有高拷贝数，表现出广泛的宿主范围，并且经常可以在细菌物种之间动员。根据复制子，RCR 质粒已被分为几个家族，其中最著名的是 pC194 和 pUB110（Rep_1 家族）、pMV158 和 pE194（Rep_2 家族）以及 pT181 和 pC221（Rep_trans 家族）。RCR 质粒的遗传特征分析包括：（i）由 DNA 松弛起始蛋白介导的复制及其与同源 DNA 起点的相互作用；（ii）滞后链复制起点；（iii）抗生素抗性基因；（iv）动员功能；（v）由蛋白质和/或反义 RNA 执行的复制控制；（vi）参与的宿主编码功能。动员功能包括转移的松弛酶起始子（Mob）、转移起点和一个或两个小辅助蛋白。存在一个松弛酶家族，即由质粒 pMV158 代表的 MOB 家族，该家族已被重新审视和更新。报告了家族秘密，例如具有未知功能的假定开放阅读框。我们得出的结论是，RCR 质粒的基础研究很重要，我们的观点考虑了一个地球的概念，因为我们应该通过降低细菌的毒性并同时尊重其遗传多样性来将细菌纳入我们的日常生活。
