Possible Synergistic Effects of Thymol and Nicotine Against Crithidia bombi Parasitism in Bumble Bees.
Possible Synergistic Effects of Thymol and Nicotine Against Crithidia bombi Parasitism in Bumble Bees.
复制标题
DOI：
10.1371/journal.pone.0144668
复制
发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Palmer-Young EC
中科院分区：
文献类型：
--
作者：
Biller OM;Adler LS;Irwin RE;McAllister C;Palmer-Young EC
花蜜含有具有抗菌特性的次级化合物，不仅可以影响植物与传粉者的相互作用，还可以影响传粉者与其寄生虫之间的相互作用。虽然最近的研究表明，食用植物次生化合物可以减少传粉者寄生虫的负荷，但对剂量或化合物组合的影响知之甚少。以凤仙花（Bombus impatiens）及其专性寄主炸弹蜂（Crithidia bombi）为研究对象，研究了花蜜化学对寄主-寄主相互作用的影响。在两个实验中，我们测试了(1)二级化合物百里香酚和尼古丁是否协同作用以减少寄生虫的寄生，(2)饲粮百里香酚浓度是否影响寄生虫的抗性。在两个试验中，均对未感染的凤仙花接种凤仙花菌，然后饲喂特殊日粮处理7 d，评估感染水平。在协同作用实验中，百里香酚和尼古丁单独或联合使用对寄生虫负荷和宿主死亡率均无显著影响。然而，与对照组相比，胸腺素-尼古丁联合治疗减少了30%的对数转化寄生虫计数（P = 0.08）。在控制百里香酚浓度的实验中，我们发现任何百里香酚浓度对豚鼠负荷都没有显著影响，但适度（2 ppm）的百里香酚浓度会导致死亡率接近显著增加（P = 0.054）。我们的结果初步表明了混合饮食对宿主免疫的价值，但与脊椎动物和其他无脊椎动物系统中饮食中百里香酚和尼古丁的抗菌活性研究进行了对比。我们建议未来的研究评估毒力的遗传变异、多菌株竞争以及与肠道微生物群落的相互作用，这些遗传变异可能介导次级化合物的抗菌活性。
Floral nectar contains secondary compounds with antimicrobial properties that can affect not only plant-pollinator interactions, but also interactions between pollinators and their parasites. Although recent work has shown that consumption of plant secondary compounds can reduce pollinator parasite loads, little is known about the effects of dosage or compound combinations. We used the generalist pollinator Bombus impatiens and its obligate gut parasite Crithidia bombi to study the effects of nectar chemistry on host-parasite interactions. In two experiments we tested (1) whether the secondary compounds thymol and nicotine act synergistically to reduce parasitism, and (2) whether dietary thymol concentration affects parasite resistance. In both experiments, uninfected Bombus impatiens were inoculated with Crithidia and then fed particular diet treatments for 7 days, after which infection levels were assessed. In the synergism experiment, thymol and nicotine alone and in combination did not significantly affect parasite load or host mortality. However, the thymol-nicotine combination treatment reduced log-transformed parasite counts by 30% relative to the control group (P = 0.08). For the experiment in which we manipulated thymol concentration, we found no significant effect of any thymol concentration on Crithidia load, but moderate (2 ppm) thymol concentrations incurred a near-significant increase in mortality (P = 0.054). Our results tentatively suggest the value of a mixed diet for host immunity, yet contrast with research on the antimicrobial activity of dietary thymol and nicotine in vertebrate and other invertebrate systems. We suggest that future research evaluate genetic variation in Crithidia virulence, multi-strain competition, and Crithidia interactions with the gut microbe community that may mediate antimicrobial activities of secondary compounds.