Diversity and Species Composition of Midgut Symbiotic Bacteria in Culex quinquefasciatus Mosquitoes in Gampaha District, Sri Lanka

Abstract

Mosquitoes, notorious for their deadly impact as disease vectors, also hold economic value due to their role in disease transmission. This study focuses on understanding mosquito gut microbiota as a foundation for innovative vector control strategies aimed at reducing disease spread. Conducted in the Gampaha Medical Officer of Health (MOH) area in Sri Lanka, the research aimed to explore microbial diversity within the midgut of Culex quinquefasciatus, an essential step to support ongoing paratransgenesis efforts. Sampling was conducted using standard mosquito collection techniques, and bacterial isolates from midgut homogenates were cultured on Plate Count Agar and identified through biochemical testing. The most abundant bacterial families were further analyzed using DNA extraction, PCR amplification, and gene sequencing for species-level identification. The study identified four bacterial families (Staphylococcaceae, Streptococcaceae, Neisseriaceae, and Moraxellaceae) in adult mosquitoes, with an additional family, Micrococcaceae, found in larvae. Notably, the relative distribution of midgut bacteria varied significantly among field-caught larval and adult strains from different study areas (chi-square = 1.673; P < 0.05), suggesting a consistent bacterial flora across mosquito life stages and geographic locations. A key finding was the detection of Lysinibacillus sphaericus, a bacterium with strong potential for use in paratransgenesis. Given the high mosquito density in the region, implementing paratransgenesis for Cx. quinquefasciatus control is recommended. Additionally, understanding gut microbial composition may enhance integration of modified microbiota into existing Sterile Insect Technique (SIT) and Incompatible Insect Technique (IIT) strategies in Sri Lanka.