Mwamburi, S. M. | Search bioRxiv

bioRxiv2026

Larval habitat bacteria emit volatile semiochemicals that modulate oviposition site selection in the malaria vector Anopheles gambiae (Diptera: Culicidae)

BackgroundLarval 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. MethodsWe 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 Students t-tests, Mann-Whitney U tests, and calculation of the Oviposition Activity Index (OAI). ResultsProteobacteria 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. ConclusionsBacterial 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 HighlightsO_LIBacteria from mosquito larval habitats influence oviposition of Anopheles gambiae. C_LIO_LISeveral bacterial isolates significantly repel gravid mosquitoes. C_LIO_LIGC-MS analysis revealed VOCs including benzenoids, ketones, phenols, and aldehydes. C_LIO_LIBacterial volatiles show potential for novel mosquito control strategies. C_LI

microbiology↗

bioRxiv2026

State of mangrove biodiversity assessment in Kenya and the prospect of environmental DNA in strengthening surveys

Assessing and monitoring biodiversity in mangrove ecosystems remains challenging, with most studies relying on proxy indicators to infer biodiversity status. This limit understanding of biodiversity dynamics and constrains evidence-based mangrove management. In the Western Indian Ocean region, biodiversity assessments in mangrove forests remain scanty, with no clear information on spatiotemporal and taxonomic coverage. Addressing these gaps requires examining existing biodiversity records and exploring complementary approaches that can broaden the scope and efficiency of biodiversity monitoring. This study assessed the current state of biodiversity assessments in mangrove forests in Kenya and evaluated the feasibility of environmental DNA (eDNA) as a complementary biodiversity monitoring tool. A systematic literature review was conducted by retrieving published sources from major academic databases using defined search terms to extract and compile taxonomic information. In addition, a snapshot eDNA survey was carried out in selected mangrove forests, where sediment and water samples were collected, processed, and analyzed using established molecular and bioinformatics pipelines. The literature review identified 26 sources documenting biodiversity across 15 mangrove forest areas, with 68% of the studies concentrated in four sites representing about 6% of mangrove cover in Kenya. A total of 1,044 unique taxa belonging to 255 families were identified, with the classes Teleostei, Aves, Chromadorea, and Malacostraca accounting for 84.5% of documented taxa. The eDNA survey detected heterogeneous taxa from multiple ecosystems, including 502 taxa belonging to 305 families. Only 67 families were common to both datasets, highlighting the complementarity of literature-based inventories and eDNA detection. While eDNA showed considerable potential to expand biodiversity detection, its application is constrained by a number of factors. Integrating eDNA as a core biodiversity monitoring tool in mangroves will require combining conventional surveys with molecular tools, developing curated regional DNA reference databases, and adopting standardized analytical frameworks.

molecular biology↗