Biology subjects

Gendrin, M.

Publications and source records attributed to Gendrin, M..

7 recordsLinked to original sources

bioRxiv2025

The microbiota affects energy production, nitrogen excretion and sterol metabolism in mosquito larvae

Mosquito larvae rely on a living microbiota for normal development because the microbiota supplies essential nutrients, particularly vitamins. Beyond vitamin provision, transcriptomic data suggest that the microbiota also supports other key nutritional processes. Here, we explored these roles by conducting a metabolomics analysis on Aedes aegypti third instar larvae following microbiota depletion. We sampled larvae and dissected guts 12- and 20-hours post-decolonization and analysed methanol-soluble metabolites using untargeted gas chromatography-mass spectrometry. Our findings reveal a pronounced impact of gut microbial presence on several metabolites involved in the tricarboxylic acid cycle and the uricolytic pathway. Germ-free larvae also had a lower quantity of cholesterol in guts and their long-chain fatty acid profile was altered in guts and whole larvae. Sterols, including cholesterol, are essential precursors for the production of the moulting hormone 20-hydroxyecdysone. We therefore tested how supplementing exogenous cholesterol affects the development of germ-free larvae. The effects proved to be highly concentration-dependent, ranging from a marginally significant increase in successful development to adulthood at low concentrations to a pronounced developmental impairment at higher concentrations. Moreover, bacteria deficient in fatty acids beta-oxidation had a significantly lower ability to support larval development. Together, the observed alterations suggest that microbiota-deprived larvae exhibit a downregulation of metabolic processes related to energy production, nitrogen excretion and sterol metabolism, likely due to the absence of microbiota-derived vitamins essential for these central metabolic functions. ImportanceMosquito larvae depend on gut microbiota for normal growth because microbes supply essential nutrients, particularly B vitamins. To explore microbial roles beyond vitamin provision, we analysed metabolic changes in Aedes aegypti larvae after microbiota removal using gas chromatography-mass spectrometry. Germ-free larvae exhibited decreased metabolites associated with the tricarboxylic acid cycle and uricolytic pathway, indicating a general slowdown in metabolic activity and nitrogen waste processing. Additionally, the absence of a microbiota affected cholesterol and fatty acid metabolism. To validate these findings, we found that supplementing germ-free larvae with low levels of cholesterol modestly improved their development. In contrast, larvae colonized with bacteria deficient in fatty acid metabolism exhibited significantly reduced developmental success. Overall, the findings show that removing the microbiota downregulates key metabolic pathways related to energy production, nitrogen excretion, and sterol metabolism, highlighting that bacterial vitamins and fatty acid degradation are vital for mosquito larval development and successful transformation into adults.

microbiology↗

bioRxiv2025

Bridging laboratory and field research: method adjustments to manipulate field-derived Aedes aegypti

Reference strains of Aedes aegypti, reared over numerous generations under laboratory conditions, are selected to fit laboratory conditions and commonly used in research due to their consistency and ease of handling. However, working exclusively with such strains may not fully reflect the traits of natural populations. While working on such strains is relevant in terms of reproducibility between labs, it is also important to perform some work on field-collected mosquitoes and their progeny to capture more representative biological and behavioural variation. In this study, we used the New Orleans reference strain as a control to adjust and evaluate methods to manipulate the F1 progeny of field-collected mosquitoes from Cayenne (French Guiana). To improve blood feeding rate, we tested the impact of several blood feeding systems for mosquitoes kept in a cage or in individual vials and adjusted starvation time. To monitor fertilization, we assessed if dissection buffer affects burst of spermatheca during dissection, whether mosquitoes were collected alive of shortly after death. The results described here may be helpful for studies on mosquito fitness, particularly on field-derived mosquitoes or on experiments requiring individual level monitoring. Author summaryAedes aegypti is the major vector of dengue virus, causing hundreds of millions of cases per year. To fight against disease transmission, mosquitoes are studied in the laboratory, notably using colonies of mosquitoes kept over decades in the laboratory. These reference strains have been selected to fit laboratory conditions and may thus not fully reflect the traits of natural populations. While working on such strains is relevant in a sake of consistency between labs and ease of handling, it is also important to work on field-collected mosquitoes and their progeny to capture more representative biological and behavioural variation. In this study, we adjusted and evaluated methods to manipulate the F1 progeny of field-collected mosquitoes from Cayenne (French Guiana), using the New Orleans reference strain as a control. To improve blood feeding rate, we tested the impact of several blood feeding systems for mosquitoes kept in a cage or in individual vials and adjusted starvation time. To monitor fertilization, we assessed if dissection buffer affects burst of spermatheca during dissection, whether mosquitoes were collected alive of shortly after death. The results described here may be helpful for studies on mosquito fitness, particularly on field-derived mosquitoes or on experiments requiring individual level monitoring.

zoology↗

bioRxiv2025

Population genomics of Anopheles darlingi, the principal South American malaria vector mosquito

Malaria in South America remains a serious public health problem. Anopheles (Nyssorhynchus) darlingi is the most important malaria vector across tropical Latin America. Vector-targeted disease control efforts require a thorough understanding of mosquito demographic and evolutionary patterns. We present and analyze whole genomes of 1094 A. darlingi (median depth 18x) from six South American countries. We observe deep geographic population structure, high genetic diversity including thirteen putative segregating inversions, and no evidence for cryptic sympatric taxa despite high interpopulation divergence. Strong signals of selection are plausibly driven by insecticides, especially on cytochrome P450 genes, one of which we validated experimentally. Our results will facilitate effective mosquito surveillance and control, while highlighting ongoing challenges that a diverse vector poses for malaria elimination in the western hemisphere.

evolutionary biology↗

bioRxiv2024

Extracellular microbes are required for mosquito development even in the presence of Wolbachia

Wolbachia is an endosymbiotic bacterium infecting a wide array of invertebrates that gained attention for its potential to curb the transmission of vector-borne diseases. Its capacity to colonize arthropod populations is generally driven by vertical transmission and reproductive manipulation. In some insect species, Wolbachia additionally became an essential nutritional symbiont, providing vitamins to its host. As mosquito larvae require microbe-derived vitamins for development, we studied whether such a support of Wolbachia would exist in mosquitoes but be masked by the presence of other microbes. We chose Culex quinquefasciatus species to address this question, as it is highly colonized with Wolbachia. We developed a method to produce Culex quinquefasciatus devoid of extracellular microbiota and demonstrated that Wolbachia alone is insufficient to support larval development. Using transient colonization with Escherichia coli, we managed to produce adult Culex quinquefasciatus harboring Wolbachia only. When curbing Wolbachia infection of these E. coli-colonized larvae via tetracycline treatment, we obtained a higher larval development. Together, our data indicate that Wolbachia does not support development but rather acts here as a metabolic burden, and that E. coli is sufficient for development success even in a species that grows in "dirty" water. This opens the way towards gnotobiology studies in Culex quinquefasciatus and highlights the complex relationships between Wolbachia and its mosquito host. Author summaryWolbachia is a bacterium infecting many invertebrates that gained attention for its potential to curb the transmission of vector-borne diseases, such as dengue. In some insect species, Wolbachia provides vitamins to its host. As mosquito larvae require microbe-derived vitamins for development, we studied whether such a support of Wolbachia would exist in mosquitoes but be masked by the presence of other microbes. We chose Culex quinquefasciatus species to address this question, as it is highly colonized with Wolbachia. We developed a method to produce Culex quinquefasciatus devoid of extracellular microbiota and demonstrated that Wolbachia alone is insufficient to support larval development. We transiently colonized these larvae with Escherichia coli to rescue larval development and to produce adults harboring Wolbachia only. When curbing Wolbachia infection of these E. coli-colonized larvae via tetracycline treatment, we obtained a higher larval development. Together, our data indicate that Wolbachia does not support development but rather acts here as a metabolic burden, and that E. coli is sufficient for development success even in a mosquito species that grows in "dirty" water.

microbiology↗

bioRxiv2023

Nutritional sex-specificity during larval development in mosquitoes

Mosquitoes rely on their microbiota for B vitamin synthesis. We previously found that Aedes aegypti third-instar larvae cleared of their microbiota were impaired in their development, notably due to a lack of folic acid (vitamin B9). In this study, we found that diet supplementation using a cocktail of seven B vitamins did not improve mosquito developmental success, but rather had a significant impact on the sex-ratio of the resulting adults, with an enrichment of female mosquitoes emerging from B vitamin-treated larvae. A transcriptomic analysis of male and female larvae identified some sex-specific regulated genes upon vitamin treatment. When treating germ-free larvae with individual B vitamins, we detected a specific toxic effect related to biotin (vitamin B7) exposure at high concentrations. We then provided germ-free larvae with varying biotin doses and showed that males are sensitive to biotin toxicity at a lower concentration than females. Gnotobiotic larvae exposed to controlled low bacterial counts or with bacteria characterized by slower growth, show a male-enriched adult population, suggesting that males require less bacteria-derived nutrients than females. These findings shed new light on sex-specific nutritional requirements and toxicity thresholds during the development of insect larvae, which impact the sex ratio of adults.

developmental biology↗

bioRxiv2022

Establishment of a colony of Anopheles darlingi from French Guiana for vector competence studies on malaria transmission

Anopheles darlingi is a major vector of both Plasmodium falciparum and Plasmodium vivax in South and Central America. However, vector competence and physiology of this mosquito species have been scarcely studied due to difficulties in rearing it in the laboratory. Here, we report the successful establishment of a robust colony, from mosquito collection in French Guiana. We describe our mosquito colonization procedure with relevant information on environmental conditions, mating ability, larval development and survival, recorded over the first six critical generations. Experimental infection showed that our An. darlingi colony has a moderate permissiveness to in vitro produced gametocytes of the P. falciparum NF54 strain originating from Africa. This colony, that has reached its 20th generation, will allow further characterization of An. darlingi life-history traits and of Plasmodium-mosquito interactions with South American malaria parasites.

microbiology↗

bioRxiv2019

Bacteria contribute to mosquito development via folate biosynthesis and energy storage

The mosquito microbiota impacts the physiology of its host and is essential for normal larval development, thereby influencing transmission of vector-borne pathogens. Germ-free mosquitoes generated with current methods show larval stunting and developmental deficits. Therefore, functional studies of the mosquito microbiota have so far mostly been limited to antibiotic treatments of emerging adults. In this study, we developed a novel approach to produce germ-free Aedes aegypti mosquitoes. It is based on reversible colonisation with bacteria genetically modified to allow complete decolonisation at any developmental stage. We show that, unlike germ-free mosquitoes previously produced using sterile diets, reversibly colonised mosquitoes show no developmental retardation and reach the same size as control adults. This allowed us to uncouple the study of the microbiota in larvae and adults. In adults, we detected no impact of bacterial colonisation on mosquito fecundity or longevity. In larvae, we performed a transcriptome analysis and diet supplementation experiments following decolonisation during the third larval instar. Our data suggest that bacteria support larval development by contributing to folate biosynthesis and by enhancing energy storage. Our study establishes a novel tool to study the microbiota in insects and deepens our knowledge on the metabolic contribution of bacteria to mosquito development.

developmental biology↗