Department of Soil and Water Science, University of Florida, Gainesville, FL, USA.
Phytopathology. 2013 Apr;103(4):352-61. doi: 10.1094/PHYTO-09-12-0237-FI.
Within soft rots, Salmonella spp. reach population densities 10- to 100-fold higher than within intact plants. The hypothesis that Salmonella spp. exchange AI-2 signals with Pectobacterium carotovorum to increase its competitive fitness was tested using mutants involved in AI-2 production (luxS) or perception (lsrACDBF or lsrG). Co-infections of a wild-type Salmonella sp. and its AI-2 mutants (at ≈3 to 10(4)) were established in green or red tomato ('FL 47' or 'Campari' for 3 or 5 days) as well as tomato co-infected with Pectobacterium (at 10(9)) or its luxS mutant. There were no significant differences in the competitive fitness of Salmonella, indicating that AI-2 signaling is not a major input in the interactions between these organisms under the tested conditions. A Salmonella lsrG::tnpR-lacZ resolvase in vivo expression technology (RIVET) reporter, constructed to monitor AI-2-related gene expression, responded strongly to the luxS deletion but only weakly to external sources of AI-2. Growth in soft rots generally decreased RIVET resolution; however, the effect was not correlated to the luxS genotype of the Pectobacterium sp. The results of this study show that AI-2 signaling offers no significant benefit to Salmonella spp. in this model of colonization of tomato or soft rots.
在软腐病中，沙门氏菌的种群密度比完整植物中的种群密度高 10-100 倍。沙门氏菌与果胶杆菌交换 AI-2 信号以增加其竞争适应性的假设通过涉及 AI-2 产生（luxS）或感知（lsrACDBF 或 lsrG）的突变体进行了测试。野生型沙门氏菌及其 AI-2 突变体（约 3 至 10(4)) 的共感染在绿色或红色番茄（3 或 5 天用“FL 47”或“Campari”）以及与果胶杆菌（10(9)) 或其 luxS 突变体共感染的番茄中建立。沙门氏菌的竞争适应性没有显著差异，表明在测试条件下，AI-2 信号不是这些生物体相互作用的主要输入。构建用于监测 AI-2 相关基因表达的沙门氏菌 lsrG::tnpR-lacZ 重组酶体内表达技术（RIVET）报告基因对 luxS 缺失反应强烈，但对外部 AI-2 源反应较弱。在软腐病中的生长通常会降低 RIVET 分辨率；然而，该效果与果胶杆菌的 luxS 基因型无关。这项研究的结果表明，在番茄或软腐病定植的这种模型中，AI-2 信号对沙门氏菌没有明显的益处。
