Midgut microbiota diversity and interactions shift when field Aedes aegypti mosquitoes carry the wMel strain of Wolbachia pipientis

The gut microbiota plays a crucial role in mosquito biology and immunity, but the effects of Wolbachia on microbiota diversity remain unclear. In Brazil, wMel-carrying Aedes aegypti were first deployed in 2015 to replace wild populations and block arbovirus transmission. We analyzed through 16S rRNA amplicon-sequencing (V3-V4 region) the midgut microbiota of field-caught wMel- and wMel + Ae. aegypti from areas of Rio de Janeiro with different wMel invasion status. Overall, wMel+ mosquitoes exhibited reduced bacterial diversity and altered microbiota composition. The interactions between bacterial taxa were also reduced in wMel+ when compared to sympatric wMel- mosquitoes from areas with partial Wolbachia introgression, suggesting a transitional microbial composition, whereas areas with full Wolbachia invasion displayed more homogeneous, densely connected bacterial communities. Although Wolbachia played a central role in microbial networks, its effects appeared contingent on other co-occurring taxa. Notably, certain bacteria such as Acetobacteraceae (Asaia), Moraxellaceae (Acinetobacter), and Xanthomonadaceae were associated with reduced wMel abundance, potentially impacting its pathogen-blocking efficiency. Targeting these interactions may enhance the success of Wolbachia-based vector control strategies.