Carvia-Hermoso Cristina, Cuéllar Virginia, Bernabéu-Roda Lydia M, van Dillewijn Pieter, Soto María J
Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain.
Plants (Basel). 2024 Feb 25;13(5):628. doi: 10.3390/plants13050628.
Type IVc Pili (T4cP), also known as Tad or Flp pili, are long thin microbial filaments that are made up of small-sized pilins. These appendages serve different functions in bacteria, including attachment, biofilm formation, surface sensing, motility, and host colonization. Despite their relevant role in diverse microbial lifestyles, knowledge about T4cP in bacteria that establish symbiosis with legumes, collectively referred to as rhizobia, is still limited. contains two clusters of T4cP-related genes: and , which are located on the chromosome and the pSymA megaplasmid, respectively. Bundle-forming pili associated with are involved in the competitive nodulation of alfalfa plants, but the role of remains elusive. In this work, we have performed a comprehensive bioinformatic analysis of T4cP genes in the highly competitive GR4 strain and investigated the role of its clusters in pilus biogenesis, motility, and in the interaction with alfalfa. Single and double -cluster mutants were constructed on the wild-type genetic background as well as in a flagellaless derivative strain. Our data demonstrate that both chromosomal and pSymA clusters are functional in pili biogenesis and contribute to surface translocation and nodule formation efficiency in GR4. In this strain, the presence of in the absence of reduces the competitiveness for nodule occupation.
IVc型菌毛（T4cP），也称为Tad菌毛或Flp菌毛，是由小型菌毛蛋白组成的细长微生物丝。这些附属物在细菌中发挥不同功能，包括附着、生物膜形成、表面感知、运动性和宿主定殖。尽管它们在多种微生物生活方式中发挥着相关作用，但关于与豆科植物建立共生关系的细菌（统称为根瘤菌）中T4cP的知识仍然有限。 含有两个与T4cP相关的基因簇： 和 ，它们分别位于染色体和pSymA大质粒上。与 相关的束状菌毛参与苜蓿植物的竞争性结瘤，但 的作用仍然难以捉摸。在这项工作中，我们对高度竞争性的GR4菌株中的T4cP基因进行了全面的生物信息学分析，并研究了其 基因簇在菌毛生物合成、运动性以及与苜蓿相互作用中的作用。在野生型遗传背景以及无鞭毛衍生菌株中构建了单簇和双簇突变体。我们的数据表明，染色体和pSymA 基因簇在菌毛生物合成中均起作用，并有助于GR4中的表面易位和结瘤形成效率。在该菌株中，在没有 的情况下存在 会降低对根瘤占据的竞争力。
