Biology subjects

Nawrot-Esposito, M.-P.

Publications and source records attributed to Nawrot-Esposito, M.-P..

5 recordsLinked to original sources

bioRxiv2025

Chronic dietary ingestion of Bacillus thuringiensis spores promotes intestinal inflammation and aging in non-target adult Drosophila

Bacillus thuringiensis (Bt), a spore-forming Gram-positive bacterium, is the leading microbial insecticide used in both organic and conventional agriculture to fight lepidopteran larvae. Bt insecticides, which consist of a mix of Bt spores and crystals of entomopathogenic toxins (Cry toxins), kill target pest larvae rapidly after ingestion by destroying their intestinal epithelium. The potential adverse effects of chronic consumption of Bt spores by non-target organisms have not been thoroughly investigated. In this study, using adult Drosophila melanogaster, a non-target dipteran organism of Bt insecticides, we show that chronic ingestion of agricultural doses of spores in the diet reduces lifespan. Our results demonstrate that Bt spore ingestion affects gut morphology, promotes dysplasia, alters septate junctions and enhances epithelial permeability. In addition, we observed increased levels of inflammatory signaling pathways and reactive oxygen species. Taken together, 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. Extended to non-target insects, which account for 85% of animal biodiversity, our study suggests that highly persistent Bt spores may have unintended long-term effects on the environment.

physiology↗

bioRxiv2024

Filopodia-like Structures are Essential for Steroid Release

Steroid hormones, crucial for development and physiology, were traditionally believed to diffuse passively through membranes. However, recent evidence shows insect steroid ecdysone being secreted via regulated exocytosis, but the mechanisms ensuring successful hormone release into circulation remain unclear. Our study identifies specialized membrane protrusions, filopodia-like structures named "hormonemes," in the Drosophila prothoracic gland as essential for steroid vesicle release. Confocal imaging reveals that these actin- and tubulin-rich structures form a membrane-intertwined basal domain critical for secretion. Disrupting filopodia by interfering with BM interactions--perlecan or {beta}-integrin--or filopodia-specific protein expression---actinin--significantly reduces ecdysone signaling by impairing its release, despite proper production in the gland. Additionally, filopodia dynamics, such as length and density, align with secretion timing and hormone circulating levels, suggesting their role in synchronizing release with physiological needs. The systematic presence of membrane protrusions in steroid-secreting glands across species prompts a comprehensive re-evaluation of steroid release mechanisms.

developmental biology↗

bioRxiv2023

Ingestion of Bacillus cereus spores dampens the immune response to favor bacterial persistence

Spores are considered as dormant entities highly resistant to extreme conditions. Among them, Bacillus cereus spores are commonly associated with foodborne outbreaks. Nevertheless, the pathological processes associated with spore ingestion and germination remain poorly understood. Here, we show that while ingestion of vegetative bacteria leads to their elimination from the midgut and small intestines of Drosophila and mice, respectively, a single ingestion of spores leads to the persistence of bacteria for at least 10 days. Using Drosophila genetics, we demonstrate that spores escape the innate immune response of the anterior midgut. Once in the posterior midgut, spores germinate, and the vegetative cells dampen the immune signaling through the induction of amidases which are negative regulators of the immune response. This study provides evidence for how B. cereus spores hijack the intestinal immune defenses allowing the localized birth of vegetative bacteria responsible for the digestive symptoms associated with foodborne illness outbreaks.

immunology↗

bioRxiv2020

Bacillus thuringiensis var. kurstaki bioinsecticide induces growth defects and developmental delay of the non-target organism Drosophila melanogaster by disturbing homeostasis of the larval intestine

Bioinsecticides made from the bacterium Bacillus thuringiensis (Bt) are the best-selling bioinsecticide worldwide. Among Bt bioinsecticides, those based on the strain Bt var. 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 doses that could be reached in the field upon sprayings, we have shown that Btk products impair growth and developmental time of the non-target dipteran Drosophila melanogaster. These effects are mediated by the synergy between Btk bacteria and Btk insecticidal toxins, which induces a significant apoptosis of larval enterocytes, resulting in a decreased intestinal capacity to digest proteins. The harmful effects can be mitigated by a protein-rich diet or by adding the probiotic bacterium Lactobacillus plantarum into the food. Finally, we showed that the larval midgut maintain its integrity upon Btk aggression thanks to both the flattening of surviving enterocytes and the generation of new immature cells arising from the adult midgut precursor cells.

physiology↗

bioRxiv2019

Adverse effects of Bacillus thuringiensis bioinsecticide on non-target Drosophila species

Biopesticides based on Bacillus thuringiensis (Bt) spores and toxins are alternate pest management solutions widely used to control insect pests. Their increasing use could lead to accumulation in the environment, hence leading to chronic exposure of non-target organisms. Here, we tested for potential non-intentional side-effects of chronic exposure to Bt biopesticide on larvae of non-target Drosophila species present in Bt-treated areas. Doses up to those recommended for field application (106 CFU/g of fly medium) had no effect on the fly development, whereas doses 10 to 100-fold higher (107-108 CFU/g) increased developmental time and decreased adult emergence rates in a dose-dependent manner and with varying effect amplitudes for all the species and strains tested. For all them, all larvae died before pupation at the highest dose tested (109 CFU/g). Focusing on D. melanogaster, delayed development and reduced emergence resulted from stage-dependent larval mortality, and fitness-related traits of adult flies emerging from surviving Bt biopesticide exposure were moderately increased. The effects of Bt biopesticide seemed to result from the spores/cleaved toxins synergy, and possibly additives. While recommended doses had no effect on non-target Drosophila species, misuse or local accumulation of Bt bioinsecticides in the environment could have non-intentional side-effects on fly populations with potential implications for their associated communities.

ecology↗