Larval Habitat Bacteria Emit Volatile Semiochemicals that Modulate Oviposition Site Selection in the Malaria Vector Anopheles gambiae (Diptera: Culicidae)

Background

Larval habitat management is increasingly recognized as a complementary strategy for malaria vector control. While bacterial communities are abundant in mosquito breeding sites, their role in shaping oviposition behavior of Anopheles gambiae (Diptera: Culicidae) remains poorly understood. This study evaluated the relative attractiveness or repellency of water infused with bacterial isolates obtained from mosquito larval habitats to gravid Anopheles gambiae .

Methods

We isolated and taxonomically characterized bacteria from 30 larval habitats in coastal Kenya using 16S rRNA sequencing. Thirty-two representative isolates were tested in two-choice oviposition bioassays with gravid An. gambiae s.s. , and volatile organic compounds (VOCs) emitted were analyzed by GC–MS. Statistical analyses included Student’s t-tests, Mann–Whitney U tests, and calculation of the Oviposition Activity Index (OAI).

Results

Proteobacteria dominated larval habitats (78%), with frequent genera including Aeromonas , Acinetobacter , Pseudomonas , Enterobacter , and Cronobacter . Most isolates exerted strong deterrent effects, with Aeromonas hydrophila , Enterobacter hormaechei , and Pseudomonas mendocina completely inhibiting oviposition (OAI = −1; 100% repellency). Other isolates such as Neobacillus drentensis and Aeromonas veronii reduced egg deposition by >85%. In contrast, a small subset ( Aquitalea pelogenes , Pseudomonas oleovorans , Cronobacter sakazakii ) showed weak, non-significant attraction (OAI = 0.15–0.23). GC–MS revealed that highly repellent isolates emitted abundant benzenoids, ketones, phenols, ethers, oxygenated heterocycles, and aldehydes.

Conclusions

Bacterial volatiles strongly modulate oviposition site selection in An. gambiae , with most isolates acting as potent repellents. These findings highlight microbial VOCs as promising candidates for novel vector control strategies targeting gravid mosquitoes. Limitations include the laboratory-based bioassay design and lack of field validation of VOC activity. Future work should identify specific bioactive compounds and evaluate their efficacy under natural conditions.

Research Highlights

• Bacteria from mosquito larval habitats influence oviposition of Anopheles gambiae .

• Several bacterial isolates significantly repel gravid mosquitoes.

• GC–MS analysis revealed VOCs including benzenoids, ketones, phenols, and aldehydes.

• Bacterial volatiles show potential for novel mosquito control strategies.