UNDERSTANDING THE ROLE OF THE MOSQUITO NUTRITIONAL YEAST AS A MEAN TO FURTHER EXPLORE THE MOSQUITO-SYMBIONT-PATHOGENS INTERACTIONS

DÍAZ NIETO LM; BERÓN CM

Congreso; VIII Congreso de Microbiología General; 2012

Many insects have evolved symbiotic associations with bacteria, fungi and yeast. Some of these interactions are of nutritional nature, where the guest provides nutrients and the host shelter; but in other cases they might have a negative effect on the host. In mosquitoes there are microorganisms living in the gut ventral diverticulum but these associations have been poorly studied. Potential benefist could apparently exist in those mosquitoes carrying yeasts. Recent molecular genetics and fluorescence in situ hybridisation work revealed the presence of the yeast in different mosquito populations and in a variety of tissues, including the reproductive system. This location is suggestive of a vertical transmission. In addition, it is known that during the development of immature stages they consume different types of micoorganisms such as algae, protozoa, invertebrate and organic detritus. With the aim to explore in more detail this association, we studied the interaction between mosquitoes and yeast, particularly focused on the development of the mosquito from the egg to the adult stage, and its offspring. We also compared larval development in mosquitoes fed off different microorganisms. In a first experiment we fed larvae of Culex pipiens with green fluorescent protein (GFP) marked yeast (Saccharomyces cerevisiae). Then we followed the presence and location of the yeast during mosquito development (four larval instars, pupae, adult and offspring eggs), using techniques of classical microbiology, amplification of the GFP gene by PCR with specific primers and experiments of fluorescence microscopy. We managed to detect GFP+ yeast in the different development stages, including adults, and using the three methods.On the other hand, neonate larvae were fed with yeast, cyanobacteria or algae in order to compare developmental times of immature stages exposed to different diets. The feeding assay showed two interesting results. On one hand, larvae that were fed yeast developed faster than those fed on algae and cyanobacteria. Moreover, only the yeast-fed larvae reached adulthood at same time of the control, while algae and cyanobacteria-fed larvae only reached the second larval stage. Our findings let us conclude that the yeast might provide essential nutrients for mosquito development and yeast is maintained until the adult stage, suggesting an essential symbiosis. Further experiments are being designed to demonstrate if the yeasts are inoculated on the egg chorion by the mother. Our next step will be to study the role of yeast on pathogens transmitted/hosted by mosquitoes.