In this study we evaluated the contribution of gut bacteria to Ae. The number of oocytes, or the size of a batch of eggs, determines the mosquito fecundity. After this time, the oocyte yolk continues to grow and assumes its final length 48 h ABF, stage that corresponds to the end of vitellogenesis. The highest release of ecdysone occurs about 16 h ABF while maximum vitellogenin synthesis is reached at 28 h ABF and this level is maintained until 32 h ABF. The yolk proteins are transported through the hemolymph and subsequently incorporated into the oocytes. Blood meal digestion also induces the synthesis of yolk proteins by the fat body, which is regulated by ecdysteroid hormones released by the ovary. The major trypsins are expressed only 8-12 h ABF and their different expression patterns indicate that regulation of protein digestion is highly complex. Trypsin-like proteinases induced by the blood meal are responsible for the majority of blood protein digestion in Ae. ![]() The lysis of RBCs, which enclose hemoglobin, the major blood protein, is the initial step of digestion. Blood ingested is stored in the posterior midgut where proteins are digested into amino acids. Vertebrate blood is a rich and unique source of proteins for mosquito anabolic processes, such as vitellogenesis and egg production. Their function in blood digestion has not been determined to date, although it is well known that the bacterial population increases substantially after blood feeding (ABF), suggesting a potential contribution to digestive process as observed in other insects. A previous study proposed that bacteria present in Aedes aegypti gut ventral diverticulum could play a role in sugar metabolism processes. However, little is known about the functional role of these microorganisms in food digestion. Recent reports have shown that these bacteria appear to strengthen the mosquito immune system and indirectly enhance protection against malaria parasites. īacteria associated with the gut of several mosquito species have been extensively studied from both laboratory-reared and wild populations. These indigenous bacteria are essential sources of carbohydrases improving digestion efficiency of plant- derived polymers such as lignin, hemicellulose and cellulose, xylan and pectin and may also contribute to lipid and protein digestion. Particularly, the role of midgut-associated bacteria in digestion of food has been demonstrated in several insect species. These microbes are involved in various physiological functions, including food digestion, nutrition, nitrogen fixation and reproduction. Insects host many microorganisms that colonize and grow inside their tissues, mainly in the digestive system. aegypti-associated bacteria as targets for mosquito control strategies. Our findings open new possibilities to investigate Ae. aegypti and its midgut bacteria work in synergism to digest a blood meal. The reduction of bacteria affected RBC lysis, subsequently retarded protein digestion, deprived mosquito from essential nutrients and, finally, oocyte maturation was affected, resulting in the production of fewer viable eggs. ![]() ![]() Mosquito fertility was restored in the second gonotrophic cycle after suspension of the antibiotic treatment, showing that the negative effects of antibiotics in blood digestion and egg production in the first gonotrophic cycle were reversible. In addition, antibiotics did not affect the survival of mosquitoes. Treatment of female mosquitoes with antibiotics affected the lysis of red blood cells (RBCs), retarded the digestion of blood proteins and reduced egg production. The antibiotics carbenicillin, tetracycline, spectinomycin, gentamycin and kanamycin, were individually offered to female mosquitoes. In this study, oral administration of antibiotics was employed in order to examine the contribution of gut bacteria to blood digestion and fecundity in Aedes aegypti. Nevertheless, the physiological significance of these bacteria for mosquitoes has not been established to date. Recent studies have shown that midgut bacteria appear to strengthen the mosquito's immune system and indirectly enhance protection from invading pathogens. These microorganisms can live and multiply in the insect, contributing to digestion, nutrition, and development of their host. The insect gut harbors a variety of microorganisms that probably exceed the number of cells in insects themselves.
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