Diversity of Culturable Aerobic Bacteria in the Midgut of Filariasis Vector, Culex quinquefasciatus Adults in Gampaha District, Sri Lanka

Abstract

Symbiotic bacteria established in mosquito gut significantly influence disease transmission, host-parasites interaction, and determination of vectorial capacity. The present study focused on screening of midgut microbial diversity of adult Culex quinquefasciatus as a fundamental pre-requirement to support the paratransgenesis process, which is progressing in Sri Lanka. Mosquito surveys were conducted from September 2022 to December 2022 at 3 sites (Kelaniya, Gampaha, and Meerigama) in the Gampaha Medical Office of Health area of Sri Lanka. Unfed adults were sacrificed using a cold shock and surface sterilization was performed using 70% ethanol followed by rinsing with Phosphate Buffer Saline (PBS). The midgut of adults was dissected and the midgut of ten individuals was pooled in sterile PBS (250 µl) to make a homogenized lysate. A dilution series (100− 10−7 ) was made from lysate and 100 µl from each dilution was plated on Plate Count Agar and pure cultures for each microbe were obtained. Isolated bacteria were subjected to 16S rRNA amplification. A total number of 4 bacterial families Staphylococcaceae, Streptococcaceae, Bacillaceae, and Moraxellaceae were identified. Family Bacillaceae (43%) and Moraxellaceae (4%) were found as the highest and least abundant bacterial families respectively. Better separation of colonies was observed at 10−3 , 10−4 , and 10−5 dilutions. Species composition was dominated by 5 major genera; Staphylococcus, Streptococcus, Lysinibacillus, Acinetobacter and Pseudomonas. Lysinibacillus sphaericus was identified as the most abundant microbial species isolated from the midgut. The relative distribution of midgut bacteria differed significantly among field-caught adult strains, collected from three different study areas. The present data strongly encourage further investigations to explore the potential usage of the microbes in paratransgenesis control approaches.