Culex pipiens L. and Culex restuans egg rafts harbor diverse bacterial communities compared to their midgut tissues

The bacterial communities associated with mosquito eggs are an essential component of the mosquito microbiota, yet there are few studies characterizing and comparing the microbiota of mosquito eggs to other host tissues. We sampled gravid female Culex pipiens and Culex restuans from the field, allowed them to oviposit in the laboratory, and characterized the microbiota associated with their egg rafts and midguts for comparison through MiSeq sequencing of the 16S rRNA gene. Results: Bacterial richness was higher in egg rafts than in midguts for both species, and higher in Cx pipiens L. than Cx. restuans. The midgut samples of Cx. pipiens and Cx. restuans were dominated by Providencia. Culex pipiens L. and Cx. restuans egg rafts samples were dominated by Ralstonia and Novosphingobium, respectively. NMDS ordination based on Bray-Curtis distance matrix revealed that egg raft samples, or midgut tissues harbored similar bacterial communities regardless of the mosquito species. Within each mosquito species, there were distinct clustering of bacterial communities between egg raft and midgut tissues. These findings expand the list of described bacterial communities associated with Cx. pipiens L. and Cx. restuans and the additional characterization of the egg raft bacterial communities facilitates comparative analysis of mosquito host tissues, providing a basis for future studies seeking to understand any functional role of microbiota in mosquito biology.