Minimally processed or fresh fruits and vegetables are unfortunately linked to an increasing number of food-borne diseases, such as salmonellosis. One of the relevant virulence factors during the initial phases of the infection process is the bacterial flagellum. Although its function is well studied in animal systems, contradictory results have been published regarding its role during plant colonization. In this study, we tested the hypothesis that Salmonella’s flagellin plays a versatile function during the colonization of tomato plants. We have assessed the persistence in plant tissues of a Salmonella enterica wild type strain, and of a strain lacking the two flagellins, FljB and FliC. We detected no differences between these strains concerning their respective abilities to reach distal, non-inoculated parts of the plant. Analysis of flagellin expression inside the plant, at both the population and single cell levels, shows that the majority of bacteria down-regulate flagellin production, however, a small fraction of the population continues to express flagellin at a very high level inside the plant. This heterogeneous expression of flagellin might be an adaptive strategy to the plant environment. In summary, our study provides new insights on Salmonella adaption to the plant environment through the regulation of flagellin expression.

中文翻译：

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沙门氏菌在植物定植过程中异质表达鞭毛蛋白。

不幸的是，最少加工或新鲜水果和蔬菜与越来越多的食源性疾病（如沙门氏菌病）有关。感染过程初期的相关毒力因素之一是细菌鞭毛。尽管已经在动物系统中对其功能进行了很好的研究，但有关其在植物定殖过程中的作用的矛盾结果却已经发表。在这项研究中，我们检验了以下假设：沙门氏菌鞭毛蛋白在番茄植物定殖过程中起着多种功能。我们评估了沙门氏菌在植物组织中的持久性野生型菌株，以及缺少两种鞭毛蛋白FljB和FliC的菌株。我们没有发现这些菌株之间关于它们到达植物的远端，未接种部位的能力的差异。对植物体内鞭毛蛋白表达的分析（包括种群和单细胞水平）表明，大多数细菌都下调了鞭毛蛋白的产生，但是，一小部分人群继续在植物体内以很高的水平表达鞭毛蛋白。鞭毛蛋白的这种异质表达可能是植物环境的一种适应策略。总之，我们的研究通过调节鞭毛蛋白表达为沙门氏菌对植物环境的适应性提供了新的见解。