Microbiological Research Center (CIMIC), Department of Biological Sciences, Universidad de Los Andes, Carrera 1 No. 18 A-12, Bogotá, 111711, Colombia.
Parasit Vectors. 2020 Feb 12;13(1):68. doi: 10.1186/s13071-020-3928-3.
Glyphosate-based herbicides are one of the most commonly used compounds to control perennial weeds around the world. This compound is very persistent in the environment and tends to filter into aquatic ecosystems, affecting non-target species such as mosquito larvae. Aedes aegypti mosquitoes are vectors of multiple arboviruses such as dengue and Zika. Glyphosate can be degraded into non-harmful environmental compounds by Lysinibacillus sphaericus, a spore forming bacterium which can also kill Ae. aegypti larvae. In this study, we assessed the effect of glyphosate concentrations, typically used in Colombia, on the entomopathogenic activity of L. sphaericus against Ae. aegypti larvae.
Bioassays and toxicity curves were performed to compare the larval mortality between different treatments with and without bacteria and glyphosate (Roundup 747®). Larvae were exposed to both bacteria and glyphosate by adding the compound on chloride-free water. Comparisons were made using both probit regression and ANOVA analysis.
ANOVA showed a significant difference in larval mortality when adding glyphosate and L. sphaericus at the same time. Thus, a positive synergic effect on larval mortality was found when L. sphaericus and glyphosate were mixed. According to probit analysis, median lethal dose (LD50) for bacterial mixture was of 10 UFC/ml and for glyphosate was 2.34 g/l.
A positive synergic effect on the mortality of larval Ae. aegypti when exposed to L. sphaericus mixture and glyphosate was found. Molecular studies focusing on the toxin production of L. sphaericus are required to understand more about this synergistic effect.
草甘膦类除草剂是世界范围内用于控制多年生杂草的最常用化合物之一。该化合物在环境中非常持久，往往会渗透到水生生态系统中，影响非目标物种，如蚊子幼虫。埃及伊蚊是登革热和寨卡等多种虫媒病毒的传播媒介。能够形成芽孢的芽孢杆菌（Lysinibacillus sphaericus）可以将草甘膦降解为无害的环境化合物，还可以杀死埃及伊蚊幼虫。在这项研究中，我们评估了哥伦比亚常用浓度的草甘膦对球形芽孢杆菌（Lysinibacillus sphaericus）针对埃及伊蚊幼虫的杀虫活性的影响。
进行生物测定和毒性曲线分析，比较不同处理组（添加和不添加细菌及草甘膦（Roundup 747®））的幼虫死亡率。通过在无氯水中添加化合物，使幼虫同时接触细菌和草甘膦。使用概率单位回归和方差分析进行比较。
方差分析显示，同时添加草甘膦和球形芽孢杆菌时，幼虫死亡率存在显著差异。因此，当球形芽孢杆菌和草甘膦混合时，发现对幼虫死亡率有积极的协同作用。根据概率单位分析，细菌混合物的半数致死剂量（LD50）为 10 UFC/ml，草甘膦为 2.34 g/l。
当暴露于球形芽孢杆菌混合物和草甘膦时，埃及伊蚊幼虫的死亡率存在积极的协同作用。需要进行聚焦于球形芽孢杆菌毒素产生的分子研究，以进一步了解这种协同作用。
