BATHUBOW

Bacillus thuringiensis (Bt), a spore-forming Gram-positive bacterium, is the leading microbial pesticide used in both organic and conventional agriculture, making it the second most widely used pesticide in the world. Commercial Bt pesticides, which consist of Bt spores that produce entomopathogenic toxins (called Cry toxins), kill target pests after ingestion by destroying their intestinal epithelium. Although studies have shown that Bt spores and toxins are not acutely toxic for non-target organisms over a short period of time, the potential adverse effects of chronic ingestion have not been studied. It is now established that the microbial population colonizing the intestine plays a central role in the development of potential inflammatory bowel diseases (IBD) and cancer. In addition, Bt belongs to the Bacillus cereus group, which is responsible for many foodborne outbreaks in humans. To our knowledge, no study has examined the impact of Bt product consumption on IBD and bowel cancers. The aim of our project is to assess whether chronic ingestion of Bt pesticides promotes or aggravates intestinal diseases. We have been using Drosophila melanogaster, a non-target organism of Bt and a valuable model for studying the impact of Bt pesticides on insects, which are known to be important for environmental health. In addition, the conservation of intestinal physiology between Drosophila and vertebrates will facilitate the transfer of knowledge to the mouse, which is a preclinical model.
We have developed a simple, direct protocol for chronic ingestion of Bt spores that mimics natural dietary exposure to an agricultural dose. Our results show that long-term consumption of Bt-contaminated food, even at low doses, significantly reduces the lifespan of Drosophila. Our findings demonstrate that Bt spores affect gut morphology, promote dysplasia, alter septate junctions and enhance epithelial permeability. They also show that Bacillus spores germinate in the gut and that the number of vegetative cells remains constant. Additionally, we observed increased levels of inflammatory signaling pathways and reactive oxygen species. Overall, our results indicate that chronic consumption of Bt spores promotes inflammation and oxidative stress, leading to premature aging of the gut and early lethality in Drosophila.