Dynamics of gut microbiota and their hemolytic activity in vector and non-vector mosquitoes before and after feeding

Background The mosquito midgut serves as a critical interface where the resident microbiota interacts with acquired pathogens following a blood meal. While some species are known to antagonize the others facilitate the multiplication and establishment of pathogens. Despite this critical interface, our understanding of the midgut microbial landscape remains incomplete. This study aims to characterize the dynamics of the gut microbiota in both unfed and post-fed states across major vector and non-vector species, with a particular focus on the prevalence of haemolytic bacterial communities. Methods Both culture-dependent and independent methods were used to determine the diversity of the gut bacterial community pre- and post-feeding. The haemolytic pattern of the culturable bacteria was determined in blood agar plates. The species richness and Shannon alpha diversity of the bacterial communities pre and post feeding were determined. Results Analysis of the haemolytic pattern showed that both haematophagous and non-haematophagous bacterial isolates were in equal proportion in unfed conditions, non-haemolytic biota dominate haematophagous mosquitoes while haemolytic communities dominate in non-hematophagous mosquitoes after feeding. The unweighted UniFrac PCoA analysis showed that feeding exerted fewer changes in the richness of the gut bacterial community of the tested mosquitoes, except Armigeres subalbatus . The weighted UniFrac PCoA analysis showed that the gut bacterial community of unfed mosquito species was clustered together, except Aedes aegypti , while after feeding, a huge change in the relative abundance was observed in Ar. subalbatus . Although the phylum Proteobacteria, Acidobacteria, Planctomycetes, Actinobacteria, Bacteroidetes, Firmicutes, Verrucomicrobia, Crenarchaeota , and Chloroflexi play a dominant role and have changed considerably after feeding, a majority of the bacterial residents are present in extremely small numbers as minor resident biota. A comparative analysis showed that the species richness of the gut bacterial community increases after feeding, while the Shannon diversity showed no change between pre and post feeding. Conclusion The present study provides a comprehensive overview of the gut bacterial community in hematophagous and non-hematophagous mosquitoes pre and post feeding. While the blood meal serves as a primary driver of taxonomic shifts, the response of haemolytic bacteria is species-specific. In general, post-feeding supports haemolytic bacteria in non-hematophagous and non-haemolytic bacteria in hematophagous mosquitoes. While feeding caused a shift in the species richness of the gut bacterial community in Ar. subalbatus and the relative abundance of gut biota changed in both Ae. aegypti and Ar. subalbatus , the changes were minimal in the rest of the species.