Bacteria Isolated from Mosquito Proliferation Sites Influence on the Oviposition Behavior in Anopheles Arabiensis (Diptera: Culicidae)

The bacterial composition of mosquito oviposition sites significantly influences egg-laying preferences, making it a critical factor in developing innovative mosquito control strategies, particularly in malaria-endemic regions like Kwale County, Kenya. However, the specific bacterial profiles that affect Anopheles arabiensis oviposition preferences remain largely unstudied. This research investigated the role of bacteria isolated from mosquito proliferation sites in Kwale County and their impact on the oviposition behavior of gravid An. arabiensis. Water samples were collected from preferred (with mosquito larvae) and non-preferred (without mosquito larvae) oviposition sites. Bacteria were isolated and identified through culture-based methods and molecular characterization using the 16S rRNA gene, with phylogenetic analysis employed to examine genetic relationships among isolates. The Oviposition Activity Index (OAI) was calculated in controlled bioassays to assess the attractiveness or repellence of these bacteria to gravid An. arabiensis. The study identified 14 bacterial isolates, with Enterobacter species showing the highest attractiveness to mosquitoes, as indicated by a higher OAI compared to Pluralibacter species. Notably, Bacillus pumilus strain RGS9 demonstrated the lowest OAI among bacteria from preferred sites, while Uncultured bacterium clone wp2, identified in non-preferred sites, exhibited a negative OAI, indicating repellence. Phylogenetic analysis revealed distinct clades, with Enterobacter sp. CDB3 and Enterobacter sp. MLB32 forming closely related clusters with high bootstrap support, highlighting their strong genetic similarity. Conversely, Pluralibacter gergoviae and Pluralibacter sp. strain SC were less attractive, as reflected by their lower OAI values compared to Enterobacter species. For example, Pluralibacter gergoviae had an OAI of 0.48, lower than the 0.84 of Enterobacter species, but higher than Uncultured bacterium clone wp2, which showed negative OAI values, indicating complete repellence. Significant differences in bacterial compositions were observed between preferred and non-preferred sites. Enterobacter species were predominantly associated with preferred sites, while Pluralibacter species were more common in non-preferred sites. Statistical analysis confirmed these differences, with OAI values showing a statistically significant distinction (p