Bioinsecticides made from the bacterium Bacillus thuringiensis (Bt) are the bestselling bioinsecticide worldwide. Among Bt bioinsecticides, those based on the strain Bt subsp. kurstaki (Btk) are widely used in farming to specifically control pest lepidopteran larvae. Although there is much evidence of the lack of acute lethality of Btk products for non-target animals, only scarce data are available on their potential non-lethal developmental adverse effects. Using a concentration that could be reached in the field upon sprayings, we show that Btk products impair growth and developmental time of the non-target dipteran Drosophila melanogaster. We demonstrate that these effects are mediated by the synergy between Btk bacteria and Btk insecticidal toxins. We further show that Btk bioinsecticides trigger intestinal cell death and alter protein digestion without modifying the food intake and feeding behavior of the larvae. Interestingly, these harmful effects can be mitigated by a protein-rich diet or by adding the probiotic bacterium Lactobacillus plantarum into the food. Finally, we unravel two new cellular mechanisms allowing the larval midgut to maintain its integrity upon Btk aggression: First the flattening of surviving enterocytes and second, the generation of new immature cells arising from the adult midgut precursor cells. Together, these mechanisms participate to quickly fill in the holes left by the dying enterocytes.

中文翻译：

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苏云金芽孢杆菌生物杀虫剂诱导非靶标果蝇幼虫的发育缺陷。

由苏云金芽孢杆菌（Btillus thuringiensis）（Bt）制成的生物杀虫剂是全球最畅销的生物杀虫剂。在Bt生物杀虫剂中，基于Bt亚种的菌株。kurstaki（Btk）被广泛用于农业中，专门防治鳞翅目害虫的幼虫。尽管有很多证据表明Btk产品对非目标动物没有急性杀伤力，但仅有很少的关于其潜在的非致命性发育不良影响的数据。使用在喷洒时可达到的浓度，我们表明Btk产品会损害非目标二萜的生长和发育时间果蝇。我们证明这些效应是由Btk细菌和Btk杀虫毒素之间的协同作用介导的。我们进一步表明，Btk生物杀虫剂可触发肠道细胞死亡并改变蛋白质消化，而不会改变幼虫的食物摄入和喂养行为。有趣的是，这些有害影响可以通过富含蛋白质的饮食或向食物中添加益生菌植物乳杆菌来减轻。最后，我们揭示了两种新的细胞机制，可以使幼虫中肠在Btk上保持其完整性侵略性：首先是存活的肠上皮细胞变平，其次是成年中肠前体细胞产生新的未成熟细胞。这些机制共同参与，以迅速填充垂死的肠上皮细胞留下的孔。