Webinar: Dr. Mathilde Gendrin

Date and Time: Monday, February 23, 2026, 15:00 CEST.

Abstract

Microbiota interactions are highly context-dependent, yet how these relationships shift across host life stages remains poorly understood in arthropods. Using gnotobiotic Aedes aegypti mosquitoes, we dissected the strain-specific effects of three bacterial isolates—Asaia bogorensis, Serratia marcescens, and Acinetobacter resistens—on host fitness. Contrary to its reported mutualistic role, our Asaia strain impaired larval development and caused adult virulence. Serratia was highly pathogenic, as expected. Strikingly, Acinetobacter functioned as a potent larval mutualist, fully rescuing development during lethal co-infections by suppressing Serratia's key toxin prodigiosin rather than through bacterial competition. However, this protection was strictly stage-specific: Acinetobacter failed to mitigate virulence in adults, which suffered reduced survival, blood-feeding, and fecundity regardless of co-infection status. Importantly, we discovered that pathogenic bacteria can override host genetic resistance to deltamethrin, rendering a resistant mosquito population susceptible—a phenotype not rescued by Acinetobacter. Together, our findings reveal that microbiota-mediated fitness effects are profoundly stage-specific and demonstrate a mutualist-driven anti-virulence mechanism, offering proof-of-concept for microbial manipulation strategies in vector control and insect rearing.
 

Speaker Bio: Mathilde Gendrin is a vector biologist at Institut Pasteur de la Guyane, where she established her lab in 2017 after PhD training at Université Pierre et Marie Curie (Paris 6) and EPFL, and a postdoc at Imperial College London. Her laboratory studies mosquito microbiota and its influence on vector-borne disease transmission through integrated field and experimental approaches. Her team focuses on key local vectors of malaria, arboviruses and lymphatic filariasis, notably Anopheles darlingi and Aedes aegypti. Their research pioneered methods for generating germ-free and gnotobiotic mosquitoes leveraging a culture collection of bacteria isolated from mosquito populations throughout French Guiana. This enables them to dissect bacterial impacts on mosquito fitness and inter-microbial dynamics, emphasizing harnessing beneficial bacterial traits for transmission-blocking strategies requiring mosquito rearing.