Microbiology Adaptation and Pathogenesis, CNRS, University of Lyon, University Claude Bernard Lyon 1, INSA Lyon, Villeurbanne, France.
Prog Mol Biol Transl Sci. 2016;142:93-129. doi: 10.1016/bs.pmbts.2016.05.006. Epub 2016 Jul 12.
Dickeya, a genus of the Enterobacteriaceae family, all cause plant diseases. They are aggressive necrotrophs that have both a wide geographic distribution and a wide host range. As a plant pathogen, Dickeya has had to adapt to a vegetarian diet. Plants constitute a large storage of carbohydrates; they contain substantial amounts of soluble sugars and the plant cell wall is composed of long polysaccharides. Metabolic functions used by Dickeya in order to multiply during infection are essential aspects of pathogenesis. Dickeya is able to catabolize a large range of oligosaccharides and glycosides of plant origin. Glucose, fructose, and sucrose are all efficiently metabolized by the bacteria. To avoid the formation of acidic products, their final catabolism involves the butanediol pathway, a nonacidifying fermentative pathway. The assimilation of plant polysaccharides necessitates their prior cleavage into oligomers. Notably, the Dickeya virulence strategy is based on its capacity to dissociate the plant cell wall and, for this, the bacteria secrete an extensive set of polysaccharide degrading enzymes, composed mostly of pectinases. Since pectic polymers have a major role in plant tissue cohesion, pectinase action results in plant rot. The pectate lyases secreted by Dickeya play a double role as virulence factors and as nutrient providers. This dual function implies that the pel gene expression is regulated by both metabolic and virulence regulators. The control of sugar assimilation by specific or global regulators enables Dickeya to link its nutritional status to virulence, a coupling that optimizes the different phases of infection.
迪凯亚是肠杆菌科的一个属,可引起植物病害。它们是具有广泛地理分布和宿主范围的侵袭性坏死营养生物。作为一种植物病原体,迪凯亚必须适应素食饮食。植物构成了大量碳水化合物的储存库;它们含有大量的可溶性糖,植物细胞壁由长的多糖组成。迪凯亚在感染过程中用于繁殖的代谢功能是发病机制的重要方面。迪凯亚能够分解大量植物来源的低聚糖和糖苷。细菌能够有效地代谢葡萄糖、果糖和蔗糖。为了避免形成酸性产物,它们的最终分解代谢涉及丁二醇途径,一种非酸化发酵途径。植物多糖的同化需要它们先被裂解成低聚物。值得注意的是,迪凯亚的毒力策略基于其分离植物细胞壁的能力,为此,细菌分泌了一套广泛的多糖降解酶,主要由果胶酶组成。由于果胶聚合物在植物组织凝聚中起主要作用,果胶酶的作用导致植物腐烂。迪凯亚分泌的果胶酸裂解酶既是毒力因子,又是营养物质的提供者。这种双重功能意味着 pel 基因的表达受到代谢和毒力调节剂的调控。通过特定或全局调节剂控制糖的同化,使迪凯亚能够将其营养状况与毒力联系起来,这种偶联优化了感染的不同阶段。