Comparative Analysis of Gut Microbiota in <i>Culex pipiens pallens</i> and <i>Culex tritaeniorhynchus</i> from Four Regions in Chinese: Composition, Function, and Antibiotic Resistance

<b><i>Background:</i></b> Understanding the composition, structure, and function of mosquito gut microbiota is critical for developing microbial-based strategies to control mosquito-borne diseases. Regional variations in gut microbial diversity and abundance may influence pathogen transmission and facilitate the dissemination of antimicrobial resistance (AMR). <b><i>Methods:</i></b> Adult Culex pipiens pallens and Culex tritaeniorhynchus mosquitoes were collected from four provinces in China. The gut microbiota was analyzed using 16S rRNA gene amplicon sequencing targeting the V3-V4 hypervariable region. Taxonomic profiles were determined at the phylum and genus levels, and functional characteristics of the gut bacterial community were inferred from 16S rRNA gene data using predictive functional profiling tools. In addition, whole-genome sequencing (WGS) was performed on 49 cultured bacterial isolates to identify antibiotic and insecticide resistance genes. <b><i>Results:</i></b> At the phylum level, Proteobacteria (49.87-99.69%) and Firmicutes (3.43-49.81%) dominated the mosquito gut microbiota. At the genus level, Wolbachia (13.67-61.96%), Acinetobacter (1.46-29.57%), Staphylococcus (0.53-37.80%), and Providencia (13.64-19.20%) were predominant. Functional profiling revealed regional variation in microbial communities, particularly in genes associated with metabolic processes. WGS analysis of bacterial isolates demonstrated a high prevalence of antibiotic resistance genes, especially those conferring multiclass resistance, whereas insecticide resistance genes were detected at lower frequencies. <b><i>Conclusion:</i></b> This study reveals significant regional differences in the composition and functional potential of mosquito gut microbiota, accompanied by widespread antimicrobial resistance among cultured isolates. These findings provide critical insights for identifying microbial targets and developing region-specific microbial or genetic control strategies for mosquito-borne diseases.