Allard Nancy, Neil Kevin, Grenier Frédéric, Rodrigue Sébastien
Département de biologie, Faculté des sciences, Université de Sherbrookegrid.86715.3d, Sherbrooke, Quebec, Canada.
Microbiol Spectr. 2022 Apr 27;10(2):e0230321. doi: 10.1128/spectrum.02303-21. Epub 2022 Mar 16.
Type IV pili (T4P) are common bacterial surface appendages involved in different biological processes such as adherence, motility, competence, pathogenesis, and conjugation. In this work, we describe the T4P of TP114, an IncI2 enterobacterial conjugative plasmid recently shown to disseminate at high rates in the mouse intestinal tract. This pilus is composed of the major PilS and minor PilV pilins that are both important for conjugation in broth and in the gut microbiota but not on a solid support. The PilV-coding sequence is part of a shufflon and can bear different C-terminal domains. The shufflon is a multiple DNA inversion system containing many DNA cassettes flanked by recombination sites that are recognized by a shufflon-specific tyrosine recombinase (shufflase) promoting the recombination between DNA segments. The different PilV variants act as adhesins that can modify the affinity for different recipient bacteria. Eight PilV variants were identified in TP114, including one that has not been described in other shufflons. All PilV variants allowed conjugative transfer with different recipient Escherichia coli strains. We conclude that the T4P carried by TP114 plays a major role in mating pair stabilization in broth as well as in the gut microbiota and that the shufflon acts as a biological switch modifying the conjugative host range specificity. Conjugative plasmids are involved in horizontal gene transfer in the gut microbiota, which constitutes an important antibiotic resistance gene reservoir. However, the molecular mechanisms used by conjugative plasmids to select recipient bacteria and transfer at high rates in the mouse gut microbiota remain poorly characterized. We studied the type IV pilus carried by TP114 and demonstrated that the minor pilin PilV acts as an adhesin that can efficiently select target cells for conjugative transfer. Moreover, the gene can be rapidly modified by a shufflon, hence modulating the nature of the recipient bacteria during conjugation. Our study highlights the role of mating pair stabilization for conjugation in broth as well as in the gut microbiome and explains how the host spectrum of a plasmid can be expanded simply by remodeling the PilV adhesin.
IV型菌毛（T4P）是常见的细菌表面附属结构，参与多种生物学过程，如黏附、运动性、感受态、致病作用和接合作用。在本研究中，我们描述了TP114的T4P，TP114是一种IncI2肠杆菌接合质粒，最近发现它能在小鼠肠道中以高频率传播。这种菌毛由主要菌毛蛋白PilS和次要菌毛蛋白PilV组成，二者对在肉汤中以及肠道微生物群中的接合作用都很重要，但在固体支持物上则不然。PilV编码序列是一个可变区的一部分，可带有不同的C末端结构域。可变区是一种多重DNA倒位系统，包含许多侧翼为重组位点的DNA盒，这些重组位点可被可变区特异性酪氨酸重组酶（可变区酶）识别，促进DNA片段之间的重组。不同的PilV变体作为黏附素，可改变对不同受体细菌的亲和力。在TP114中鉴定出了8种PilV变体，其中一种在其他可变区中尚未见报道。所有PilV变体都能与不同的受体大肠杆菌菌株进行接合转移。我们得出结论，TP114携带的T4P在肉汤以及肠道微生物群中的配对稳定中起主要作用，可变区作为一种生物学开关，可改变接合宿主范围特异性。接合质粒参与肠道微生物群中的水平基因转移，肠道微生物群是重要的抗生素抗性基因库。然而，接合质粒在小鼠肠道微生物群中选择受体细菌并以高频率转移所使用的分子机制仍知之甚少。我们研究了TP114携带的IV型菌毛，证明次要菌毛蛋白PilV作为一种黏附素，可有效选择用于接合转移的靶细胞。此外，该基因可被可变区快速修饰，从而在接合过程中调节受体细菌的性质。我们的研究突出了配对稳定在肉汤以及肠道微生物群接合中的作用，并解释了如何通过重塑PilV黏附素简单地扩大质粒的宿主谱。
