Li Yaxin, Hao Guixia, Galvani Cheryl D, Meng Yizhi, Fuente Leonardo De La, Hoch H C, Burr Thomas J
Department of Plant Pathology, Cornell University - New York State Agricultural Experiment Station, Geneva, NY 14456, USA.
Microbiology (Reading). 2007 Mar;153(Pt 3):719-726. doi: 10.1099/mic.0.2006/002311-0.
Xylella fastidiosa, an important phytopathogenic bacterium, causes serious plant diseases including Pierce's disease of grapevine. It is reported here that type I and type IV pili of X. fastidiosa play different roles in twitching motility, biofilm formation and cell-cell aggregation. Type I pili are particularly important for biofilm formation and aggregation, whereas type IV pili are essential for motility, and also function in biofilm formation. Thirty twitching-defective mutants were generated with an EZ : : TN transposome system, and several type-IV-pilus-associated genes were identified, including fimT, pilX, pilY1, pilO and pilR. Mutations in fimT, pilX, pilO or pilR resulted in a twitch-minus phenotype, whereas the pilY1 mutant was twitching reduced. A mutation in fimA resulted in a biofilm-defective and twitching-enhanced phenotype. A fimA/pilO double mutant was twitch minus, and produced almost no visible biofilm. Transmission electron microscopy revealed that the pili, when present, were localized to one pole of the cell. Both type I and type IV pili were present in the wild-type isolate and the pilY1 mutant, whereas only type I pili were present in the twitch-minus mutants. The fimA mutant produced no type I pili. The fimA/pilO double mutant produced neither type I nor type IV pili.
木质部难养菌（Xylella fastidiosa）是一种重要的植物致病细菌，可引发包括葡萄皮尔斯病在内的严重植物病害。本文报道，木质部难养菌的I型菌毛和IV型菌毛在颤动运动、生物膜形成及细胞间聚集过程中发挥不同作用。I型菌毛对生物膜形成和聚集尤为重要，而IV型菌毛对运动至关重要，且在生物膜形成中也发挥作用。利用EZ::TN转座体系统构建了30个颤动缺陷型突变体，并鉴定出几个与IV型菌毛相关的基因，包括fimT、pilX、pilY1、pilO和pilR。fimT、pilX、pilO或pilR的突变导致颤动缺陷型表型，而pilY1突变体的颤动能力减弱。fimA突变导致生物膜缺陷和颤动增强表型。fimA/pilO双突变体为颤动缺陷型，几乎不产生可见生物膜。透射电子显微镜显示，菌毛（若存在）定位于细胞的一极。野生型菌株和pilY1突变体中均存在I型和IV型菌毛，而颤动缺陷型突变体中仅存在I型菌毛。fimA突变体不产生I型菌毛。fimA/pilO双突变体既不产生I型菌毛也不产生IV型菌毛。
