Mosquito-borne bacterial communities are shaped by their insect host species, geography and developmental stage. Mosquito-borne bacterial communities are shaped by their insect host species, geography and developmental stage

Mosquitoes harbour diverse bacterial communities that are influenced by geography, host species, and developmental stage. Understanding these microbiomes is crucial for assessing their role as vectors and in pathogen dissemination. Here, we compare the bacterial communities of Aedes albopictus and Aedes japonicus across eight countries: six in Europe, the USA, and Japan, using 16S rRNA amplicon sequencing. We find large differences in microbiota composition between mosquito species, with A. albopictus exhibiting lower bacterial diversity than A. japonicus. Geographic variation in bacterial diversity was also evident, with mosquitoes from Japan and the Netherlands harboring the most diverse microbiomes, while Austrian populations displayed the lowest diversity. Developmental stage hads the strongest influence on bacterial composition, with aquatic-associated genera such as Limnohabitans and Hydrogenophaga dominating larvae, whereas adult mosquitoes harbored higher abundances of Acinetobacter and Methylobacterium. No influence of within Aedes species phylogeny on the bacteriome could be observed. A number of bacterial genera with known pathogenic potential, including Pseudomonas, Serratia, Klebsiella, and Acinetobacter, were detected across multiple locations, suggesting that mosquitoes could serve as environmental reservoirs for opportunistic and antimicrobial-resistant bacteria. These findings provide insights into the ecological and epidemiological implications of mosquito microbiomes and emphasize the need for further investigation into their role in pathogen transmission and antimicrobial resistance dissemination.