School of Life Sciences, North Maharashtra University, Post Box 80, Jalgaon, 425001, Maharashtra, India.
Parasitol Res. 2012 May;110(5):1841-7. doi: 10.1007/s00436-011-2708-6. Epub 2011 Nov 9.
The tremendous worldwide efforts to isolate novel mosquito larvicidal bacteria with improved efficacy present significant promise to control vector-borne diseases of public health importance. In the present study, two native bacterial isolates, Bacillus thuringiensis (Bt SV2) and Serratia species (SV6) were evaluated for mosquito larvicidal potential against the early fourth instar larvae of Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus with reference to B. thuringiensis subsp. israelensis (Bti) H 14. The native Gram-positive, spore-forming Bt SV2 isolate showed 100% mortality against early fourth instars of Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus, in parallel to Bti H14 strain. After 24 h, Bt SV2 showed 98%, 89%, and 80.67%, and Bti H14 showed 92%, 98.33%, and 60% mortality against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus, respectively. Serratia SV6 showed highest activity against Culex quinquefasciatus (100%) followed by Anopheles stephensi (95%) and Aedes aegypti (91%) after 48 h of exposure. The Gram-negative Serratia SV6 showed delayed toxicity compared to Bti H14 and Bt SV2 against early fourth instars of Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. The relative mortality of all treatments after 12-h exposures showed the varied toxicity with respect to exposure time, bacterial treatment, and mosquito species. Genetic relatedness of the strains was confirmed on the basis of phylogenetic reconstructions based on alignment of 16S rRNA gene sequences which indicated a strong clustering of the strain SV2 with B. thuringiensis and the strain SV6 with Serratia nematodiphila. In conclusion, the native isolate B. thuringiensis SV2 showed significant toxicity while Serratia SV6 showed less and delayed toxicity against several mosquito species compared with BtiH14. They may be used as novel bacterial insecticidal agents in mosquito vector-borne disease control. To our knowledge, this is the first report on mosquito larvicidal potential of Serratia species.
为了控制具有重要公共卫生意义的媒介传播疾病，全世界正在大力分离具有增效作用的新型杀蚊细菌。本研究评估了两种本土细菌分离株，苏云金芽孢杆菌（Bt SV2）和沙雷氏菌（SV6）对埃及伊蚊、致倦库蚊和三带喙库蚊初孵 4 龄幼虫的杀蚊潜力，并与苏云金芽孢杆菌亚种以色列亚种（Bti）H14 进行了比较。本土革兰氏阳性、芽孢形成的 Bt SV2 分离株对埃及伊蚊、致倦库蚊和三带喙库蚊的初孵 4 龄幼虫表现出 100%的死亡率，与 Bti H14 株相当。24 小时后，Bt SV2 对埃及伊蚊、致倦库蚊和三带喙库蚊的死亡率分别为 98%、89%和 80.67%，而 Bti H14 分别为 92%、98.33%和 60%。沙雷氏菌 SV6 对三带喙库蚊的活性最高（100%），其次是致倦库蚊（95%）和埃及伊蚊（91%），暴露 48 小时后。与 Bti H14 和 Bt SV2 相比，革兰氏阴性沙雷氏菌 SV6 对埃及伊蚊、致倦库蚊和三带喙库蚊的初孵 4 龄幼虫的毒性延迟。所有处理在 12 小时暴露后的相对死亡率表明，细菌处理和蚊种对暴露时间的毒性存在差异。根据 16S rRNA 基因序列比对构建的系统发育重建证实了菌株的遗传相关性，这表明 SV2 株与苏云金芽孢杆菌和 SV6 株与杀线虫沙雷氏菌聚集成强簇。总之，与 BtiH14 相比，本土苏云金芽孢杆菌 SV2 对几种蚊种表现出显著的毒性，而沙雷氏菌 SV6 的毒性较低且延迟。它们可能被用作新型细菌性昆虫杀虫剂来控制蚊虫传播的疾病。据我们所知，这是首次报道沙雷氏菌对蚊虫的杀幼虫作用。
