THE NEGLECTED TENANTS: A GLIMPSE INTO FUNGAL SYMBIOSES OF MOSQUITOES

INTRODUCTION: Understanding composition and function of mosquito microbial communities can pro- vide pivotal information on insect biology, such as their environmental adaptation or vectorial capability. while an increasing number of studies have focused on bacteria, the fungal community (mycobiota) has been largely neglected, but recent studies show the presence of an important fungal diversity in mosquitoes (Malassigné et al., 2020. Pathogens, 9:564). Mosquito-mycobiota is mainly composed of Ascomycota, which comprise filamentous fungi (Pezizomycotina) and yeasts (Saccharomycotina) such as Candida, Meyerozyma, pichia, and Wickerhamomyces, that adapt to survive in the insect gut and different mutualistic yeast-insect symbioses based on trophic interdependence have been described. Yeasts generate signals of sugar resources through metabolic pathways that produce compounds, such as fermentative volatile compounds (vOCs) that attract insects. Yeasts are important not only for at- traction to food, they influence oviposition sites and larval development, but also supply diet integration of adults providing organic nitrogen, essential vitamins, and lipids (Stefanini, 2018. Yeast, 35:315-330). Lastly, fungi can exert antimicrobial properties and defence of the host (Cappelli et al., 2021. Front Mi- crobiol, 11:621605). MATERIALS AND METHODS: The mycobiota of mosquitoes (Anopheles, Aedes, and Culex) were analysed using different approaches including molecular and culture-dependent methods, and metage- nomics analysis. Larvae, adult and water samples from breeding sites were analysed providing a list of dozens fungal species associated with different mosquito species. A collection of about fifty fungal iso- lates was molecularly and biochemically characterised. Selected fungal strains have been processed by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry to extract and analyse the yeast volatile organic compounds (vOCs). based on the profile of vOCs yeast strains were tested for attractivity to gravid mosquitoes. Antimicrobial activity of yeast has been char- acterised and tested against plasmodium berghei in Anopheles stephensi. RESULTS AND CONCLUSIONS: Research outcomes are: i) Isolation of mosquito-fungal symbionts able to attract female mosquitoes; ii) Implementation of fungal blends to be combined with bio-larvicides for ‘lure and kill’ formulations to be released in mosquito breeding sites; iii) Identification of symbiotic fungi that impair the malaria parasite in vector mosquitoes; iv) basic knowledge of yeast based killer activity against mosquito-borne pathogens; v) basic knowledge of bacterial/fungal interactions in the mosquito host; vi) Formulability of fungal products to be used in field; vii) Safety assessment of fungal formulations. Such innovative fungal-based products might contribute to the control of mosquitoes and/or the diseases they transmit through very promising ‘ready to use’ technologies.