Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris, France.
Sorbonne Université, Collège doctoral, F-75005 Paris, France.
Nucleic Acids Res. 2021 Jun 4;49(10):5654-5670. doi: 10.1093/nar/gkab412.
Integrons confer a rapid adaptation capability to bacteria. Integron integrases are able to capture and shuffle novel functions embedded in cassettes. Here, we investigated cassette recruitment in the Vibrio cholerae chromosomal integron during horizontal transfer. We demonstrated that the endogenous integrase expression is sufficiently triggered, after SOS response induction mediated by the entry of cassettes during conjugation and natural transformation, to mediate significant cassette insertions. These insertions preferentially occur at the attIA site, despite the presence of about 180 attC sites in the integron array. Thanks to the presence of a promoter in the attIA site vicinity, all these newly inserted cassettes are expressed and prone to selection. We also showed that the RecA protein is critical for cassette recruitment in the V. cholerae chromosomal integron but not in mobile integrons. Moreover, unlike the mobile integron integrases, that of V. cholerae is not active in other bacteria. Mobile integrons might have evolved from the chromosomal ones by overcoming host factors, explaining their large dissemination in bacteria and their role in antibioresistance expansion.
整合子赋予细菌快速适应能力。整合子整合酶能够捕获和重组嵌入在盒式元件中的新功能。在这里，我们研究了水平转移过程中霍乱弧菌染色体整合子中的盒式元件募集。我们证明，在接合和自然转化过程中盒式元件进入引发 SOS 反应后，内源性整合酶表达被充分触发，从而介导显著的盒式元件插入。尽管整合子阵列中有大约 180 个 attC 位点，但这些插入优先发生在 attIA 位点。由于 attIA 位点附近存在启动子，所有这些新插入的盒式元件都被表达，并易于选择。我们还表明，RecA 蛋白对于霍乱弧菌染色体整合子中的盒式元件募集至关重要，但对于移动整合子则不然。此外，与移动整合子整合酶不同，霍乱弧菌的整合酶在其他细菌中没有活性。移动整合子可能是通过克服宿主因素从染色体整合子进化而来的，这解释了它们在细菌中的广泛传播及其在抗药性扩张中的作用。
