Michigan State University, Department of Plant Pathology, 103 Center for Integrated Plant Systems, East Lansing, MI 48824, USA.
Appl Environ Microbiol. 2011 Oct;77(19):7031-9. doi: 10.1128/AEM.05138-11. Epub 2011 Aug 5.
Biofilm formation plays a critical role in the pathogenesis of Erwinia amylovora and the systemic invasion of plant hosts. The functional role of the exopolysaccharides amylovoran and levan in pathogenesis and biofilm formation has been evaluated. However, the role of biofilm formation, independent of exopolysaccharide production, in pathogenesis and movement within plants has not been studied previously. Evaluation of the role of attachment in E. amylovora biofilm formation and virulence was examined through the analysis of deletion mutants lacking genes encoding structures postulated to function in attachment to surfaces or in cellular aggregation. The genes and gene clusters studied were selected based on in silico analyses. Microscopic analyses and quantitative assays demonstrated that attachment structures such as fimbriae and pili are involved in the attachment of E. amylovora to surfaces and are necessary for the production of mature biofilms. A time course assay indicated that type I fimbriae function earlier in attachment, while type IV pilus structures appear to function later in attachment. Our results indicate that multiple attachment structures are needed for mature biofilm formation and full virulence and that biofilm formation facilitates entry and is necessary for the buildup of large populations of E. amylovora cells in xylem tissue.
生物膜的形成在果胶杆菌的发病机制和植物宿主的系统侵染中起着关键作用。已经评估了胞外多糖果胶寡糖和纤维二糖在发病机制和生物膜形成中的功能作用。然而，生物膜的形成（不依赖于胞外多糖的产生）在发病机制和植物体内运动中的作用以前尚未得到研究。通过分析缺乏假定在表面附着或细胞聚集中起作用的结构的基因缺失突变体，评估了附着在果胶杆菌生物膜形成和毒力中的作用。根据计算机分析选择了研究的基因和基因簇。显微镜分析和定量测定表明，菌毛和纤毛等附着结构参与了果胶杆菌对表面的附着，并且是成熟生物膜产生所必需的。时程测定表明，I 型菌毛在附着中较早起作用，而 IV 型菌毛结构在附着中似乎较晚起作用。我们的结果表明，成熟生物膜形成和完全毒力需要多种附着结构，并且生物膜形成有助于进入并对木质部组织中大量果胶杆菌细胞的积累是必需的。
