Insect pathogenic fungus interacts with the gut microbiota to accelerate mosquito mortality

Area of Science:

• Insect pathology
• Microbial ecology
• Host-pathogen interactions

Background:

• The insect gut microbiota influences host interactions with pathogens.
• Entomopathogenic fungi infect insects via the cuticle, unlike ingested pathogens.
• The role of gut microbiota in fungal pathogenesis is largely unknown.

Purpose of the Study:

• To investigate the interaction between the gut microbiota and entomopathogenic fungi in mosquitoes.
• To elucidate the mechanisms by which gut microbiota affects fungal pathogenesis.

Main Methods:

• Topical infection of mosquitoes with Beauveria bassiana.
• Comparison of mortality rates between mosquitoes with and without gut microbiota.
• Analysis of gut microbiota composition and bacterial load post-infection.
• Gene expression analysis of antimicrobial peptides and dual oxidase (Duox).

Main Results:

• Mosquitoes with gut microbiota exhibited significantly faster mortality after B. bassiana infection.
• Fungal infection induced gut dysbiosis, increasing bacterial load and decreasing diversity.
• Serratia marcescens overgrowth in the midgut and translocation to hemocoel enhanced fungal killing.
• B. bassiana toxin oosporein down-regulated Duox expression in the mosquito midgut.

Conclusions:

• The gut microbiota significantly contributes to B. bassiana-induced mosquito mortality.
• Fungal infection disrupts gut homeostasis, favoring opportunistic bacterial pathogens.
• Oosporein-mediated Duox suppression is a key mechanism in fungal pathogenesis.