Departament de Genètica i Microbiologia, Facultat de Biociènces, Universitat Autònoma de Barcelona, Cerdanyola del Vallès (Barcelona), Catalonia, Spain.
Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Cerdanyola del Vallès (Barcelona), Catalonia, Spain.
mSphere. 2020 Mar 4;5(2):e00740-19. doi: 10.1128/mSphere.00740-19.
is a bacterial plant pathogen causing important economic losses worldwide. In addition to the polar flagella responsible for swimming motility, this pathogen produces type IV pili (TFP) that govern twitching motility, a flagellum-independent movement on solid surfaces. The implication of chemotaxis in plant colonization, through the control flagellar rotation by the proteins CheW and CheA, has been previously reported in In this work, we have identified in this bacterium homologues of the and genes, suggested to play roles in TFP-associated motility analogous to those played by the and genes, respectively. We demonstrate that strains with a deletion of the or the coding region show normal swimming and chemotaxis but altered biofilm formation and reduced twitching motility, transformation efficiency, and root attachment. Furthermore, these mutants displayed wild-type growth and impaired virulence on tomato plants after soil-drench inoculations but not when directly applied to the xylem. Comparison with deletion mutants for and -encoding the major pilin and flagellin subunits, respectively-showed that both twitching and swimming are required for plant colonization and full virulence. This work proves for the first time the functionality of a pilus-mediated pathway encoded by - genes in , demonstrating that and genes are bona fide motility regulators controlling twitching motility and its three related phenotypes: virulence, natural transformation, and biofilm formation. Twitching and swimming are two bacterial movements governed by pili and flagella. The present work identifies for the first time in the Gram-negative plant pathogen a pilus-mediated chemotaxis pathway analogous to that governing flagellum-mediated chemotaxis. We show that regulatory genes in this pathway control all of the phenotypes related to pili, including twitching motility, natural transformation, and biofilm formation, and are also directly implicated in virulence, mainly during the first steps of the plant infection. Our results show that pili have a higher impact than flagella on the interaction of with tomato plants and reveal new types of cross-talk between the swimming and twitching motility phenotypes: enhanced swimming in bacteria lacking pili and a role for the flagellum in root attachment.
是一种导致全球重大经济损失的细菌植物病原体。除了负责游动运动的极鞭毛外，该病原体还产生 IV 型菌毛（TFP），控制在固体表面上的蠕动运动，这是一种与鞭毛无关的运动。通过 CheW 和 CheA 蛋白控制鞭毛旋转，趋化作用在植物定殖中的作用已在 中报道。在这项工作中，我们在该细菌中鉴定了 和 基因的同源物，这些基因被认为在 TFP 相关运动中发挥作用，类似于 和 基因分别发挥的作用。我们证明，缺失 或 编码区域的 菌株表现出正常的游泳和趋化性，但生物膜形成和蠕动运动、转化效率和根附着减少。此外，这些突变体在土壤淋溶接种后表现出野生型生长和对番茄植物的毒力降低，但直接应用于木质部时则没有。与缺失突变体的比较 和 分别编码主要菌毛和鞭毛亚基的基因-表明，植物定殖和完全毒力都需要蠕动和游泳。这项工作首次证明了 - 编码的菌毛介导途径在 中的功能，证明了 和 基因是真正的运动调节剂，控制蠕动运动及其三种相关表型：毒力、自然转化和生物膜形成。蠕动和游泳是两种由菌毛和鞭毛控制的细菌运动。本工作首次在革兰氏阴性植物病原体 中鉴定出一种类似于鞭毛介导趋化作用的菌毛介导趋化途径。我们表明，该途径中的调节基因控制与菌毛相关的所有表型，包括蠕动运动、自然转化和生物膜形成，并且还直接参与毒力，主要是在植物感染的早期步骤。我们的结果表明，菌毛比鞭毛对 与番茄植物的相互作用的影响更大，并揭示了游动和蠕动运动表型之间的新类型串扰：缺乏菌毛的细菌中游泳增强，以及鞭毛在根附着中的作用。
