Mosquito shapes its microbiome but not its mycobiome

The microbiota of mosquitoes has emerged as a key determinant of their vectorial capacity and may modulate the ability of these vector-borne pathogens to infect mosquitoes. Midgut bacteria and fungi can interact directly or indirectly with vectored pathogens. Surprisingly, both the specific microbes that stably colonize the mosquito midgut and how the midgut shapes its microbial community remain poorly understood. In this study, we analyzed the midgut microbiome of the insect vector Aedes albopictus at three different developmental stages collected from the field. Additionally, we reared field-collected larvae under laboratory conditions, using either field water from the breeding habitat or sterilized water, to track the linear evolution of the microbiome from larvae to adulthood. Our metagenomic analysis revealed that the host environment strongly influenced the composition of the gut bacteriome by selecting specific species, while the fungal community remained virtually identical to that of the surrounding water. We identified 42 core bacterial species that form a highly interactive network, as well as two core fungal species, both of which were consistently more abundant in the mosquito gut than in the surrounding water across all life stages in both lab and field conditions. Furthermore, we successfully assembled 271 bacterial genomes de novo, 14 of which belonged to core species. These 14 bacterial genomes were enriched in genes associated with antioxidant function and cAMP metabolism. This study uncovers fluctuating bacterial dynamics alongside stable fungal communities in the mosquito gut, suggesting distinct mechanisms that shape the bacteriome and mycobiome.