Department of Entomology, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
Department of Plant Pathology, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
PLoS One. 2021 Feb 19;16(2):e0247325. doi: 10.1371/journal.pone.0247325. eCollection 2021.
The human enteric bacterial pathogen Salmonella enterica causes approximately 1.35 million cases of food borne illnesses annually in the United States. Of these salmonellosis cases, almost half are derived from the consumption of fresh, raw produce. Although epiphytic S. enterica populations naturally decline in the phyllosphere, a subset of phytophagous insects have recently been identified as biological multipliers, consequently facilitating the growth of bacterial populations. We investigated whether tomato leaves with macroscopic feeding damage, caused by infestation of adult Western flower thrips (Frankliniella occidentalis), support higher S. enterica populations. To explore this hypothesis, we assessed S. enterica populations in response to thrips feeding by varying insect density, plant age, and the gender of the insect. As a reference control, direct leaf damage analogous to thrips feeding was also evaluated using directed, hydraulic pressure. In a supplementary set series of experiments, groups of F. occidentalis infested tomato plants were later inoculated with S. enterica to determine how prior insect infestation might influence bacterial survival and persistence. Following an infestation period, leaves visibly damaged by adult F. occidentalis supported significantly higher S. enterica populations and resulted in greater amounts of electrolyte leakage (measured as electrical conductivity) than leaves lacking visible feeding damage. Plant age did not significantly influence S. enterica populations or estimates of electrolyte leakage, independent of initial infestation. Additionally, the gender of the insect did not uniquely influence S. enterica population dynamics. Finally, applications of aggressive water bombardment resulted in more electrolyte leakage than leaves damaged by F. occidentalis, yet supported comparable S. enterica populations. Together, this study indicates that F. occidentalis feeding is one of the many potential biological mechanisms creating a more habitable environment for S. enterica.
人类肠道致病菌沙门氏菌每年在美国导致约 135 万例食源性疾病。在这些沙门氏菌病例中，近一半来自食用新鲜的、生的农产品。尽管附着在植物表面的沙门氏菌自然会在叶际中减少，但最近发现一些植食性昆虫是生物倍增器，因此促进了细菌种群的生长。我们研究了是否因成虫西花蓟马（Frankliniella occidentalis）的侵害而导致番茄叶片出现肉眼可见的取食损伤，是否会支持更高的沙门氏菌种群。为了探索这一假说，我们通过改变昆虫密度、植物年龄和昆虫性别来评估昆虫取食对沙门氏菌种群的影响。作为参考对照，我们还通过定向水力压力评估了类似于西花蓟马取食的直接叶片损伤对沙门氏菌种群的影响。在一系列补充实验中，一组受西花蓟马侵害的番茄植株随后被接种沙门氏菌，以确定先前的昆虫侵害可能如何影响细菌的存活和持续存在。在侵害期结束后，与没有可见取食损伤的叶片相比，明显受到成虫西花蓟马侵害的叶片支持更高的沙门氏菌种群，并且导致更多的电解质泄漏（用电导率测量）。植物年龄对沙门氏菌种群或电解质泄漏的估计没有显著影响，而与初始侵害无关。此外，昆虫的性别也不会独特地影响沙门氏菌种群动态。最后，强烈的水冲击应用导致的电解质泄漏比西花蓟马造成的叶片损伤更多，但支持的沙门氏菌种群相当。总的来说，这项研究表明，西花蓟马的取食是为沙门氏菌创造更宜居环境的许多潜在生物学机制之一。
