NUTRITIONAL AND SYMBIONT MICROORGANISMS TO BE USED IN BIOLOGICAL CONTROL OF MOSQUITOES OF PUBLIC HEALTH IMPORTANCE

DÍAZ NIERO LM; BERÓN CM

Congreso; X CONGRESO ARGENTINO DE MICROBIOLOGIA GENERAL SAMIGE; 2014

Some microorganisms are crucial for insect nutrition, as they provide of specific nutrients like vitamins and essential amino acids. The elimination of nutritional and symbionts microorganisms indispensable for the maintenance and development of the insects could be a strategy for biological vector control, and is defined as Symbiotic Control. In a previous work, we evaluated the nutritional quality of different microorganisms (cyanobacteria, algae, yeasts and intestinal bacteria of mosquito) on Culex pipiens larvae, among them, only yeasts allowed mosquitoes to complete development until adult stage. Based on these results and the previous evidence in other insects that some yeast species could be inherited to progeny as the first food of neonate larva, we followed the presence of green fluorescence from GFP-labeled Saccharomyces cerevisiae as a sole source of food provided to C. pipiens first instar larvae. Mosquito?s four larval instars, pupae, adult as well as offspring eggs (F1) were screened for this yeast by its growth in appropriate culture medium, by fluorescence microscopy of GFP-labeled yeast and PCR amplification of the GFP gene and of the yeast 18S rRNA with generic primers. We only detected fluorescent yeast until fourth instar larvae and GFP gene until adult females. F1 eggs did not indicate the presence of S. cerevisiae (not detected by PCR). However, we still obtained some other microorganisms that grew in a suitable culture medium. Based on these results, the aims of this work were to identify those different microorganisms and to analyze if they are inoculated by the mosquito female onto the eggs. The sequences obtained by the amplification of the DNA fragments with specific or degenerate 18S rDNA primers for yeast did not allow the identification of any yeasts. On the other hand amplification of the 16S rDNA gene of these microorganisms led to the identification of bacteria belonging to the genus Acinetobacter sp. and Klebsiella sp.In addition, we detected both bacteria genera in mosquito guts, by the amplification of 16S rDNA fragments. In order to detect if these bacteria were inoculated onto the eggs by the mosquito female, we reared mosquitoes in sterile and controlled conditions, to rule out the possibility of the contamination of eggs by environmental bacteria. This assay confirms the presence of both bacteria only onto F1 eggs. This suggests that the mosquito female might inoculate the F1 eggs. However, further experiments using other rearing techniques should be performed to confirm this hypothesis, and thus to determine whether these organisms could be used in biological control programs of mosquito populations. This can be carried out by elimination of bacteria that are fundamental for mosquito nutrition, or by expression of mosquitocidal toxins in those microorganisms.