Background: The insect gut harbors a variety of microorganisms that probably exceed the number of cells in insects themselves. These microorganisms can live and multiply in the insect, contributing to digestion, nutrition, and development of their host. Recent studies have shown that midgut bacteria appear to strengthen the mosquito's immune system and indirectly enhance protection from invading pathogens. Nevertheless, the physiological significance of these bacteria for mosquitoes has not been established to date. 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. Results: The antibiotics carbenicillin, tetracycline, spectinomycin, gentamycin and kanamycin, were individually offered to female 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. In addition, antibiotics did not affect the survival of mosquitoes. 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. Conclusions: 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. These results indicate that Ae. aegypti and its midgut bacteria work in synergism to digest a blood meal. Our findings open new possibilities to investigate Ae. aegypti-associated bacteria as targets for mosquito control strategies.

We show for the first time that the ventral diverticulum of the mosquito gut (impermeable sugar storage organ) harbors microorganisms. The gut diverticulum from newly emerged and non-fed Aedes aegypti was dissected under aseptic conditions, homogenized and plated on BHI medium. Microbial isolates were identified by sequencing of 16S rDNA for bacteria and 28S rDNA for yeast. A direct DNA extraction from Ae. aegypti gut diverticulum was also performed. The bacterial isolates were: Bacillus sp., Bacillus subtilis and Serratia sp. The latter was the predominant bacteria found in our isolations. The yeast species identified was Pichia caribbica.

Background: The mosquitoA. aegyptiis vector of dengue and other viruses. New methods of vector control are needed and can be achieved by a better understanding of the life cycle of this insect. Embryogenesis is a part ofA. aegyptylife cycle that is poorly understood. In insects in general and in mosquitoes in particular energetic metabolism is well studied during oogenesis, when the oocyte exhibits fast growth, accumulating carbohydrates, lipids and proteins that will meet the regulatory and metabolic needs of the developing embryo. On the other hand, events related with energetic metabolism duringA. aegyptiembryogenesis are unknown.Results: Glucose metabolism was investigated throughoutAedes aegypti(Diptera) embryonic development. Both cellular blastoderm formation (CBf, 5 h after egg laying - HAE) and germ band retraction (GBr, 24 HAE) may be considered landmarks regarding glucose 6-phosphate (G6P) destination. We observed high levels of glucose 6-phosphate dehydrogenase (G6PDH) activity at the very beginning of embryogenesis, which nevertheless decreased up to 5 HAE. This activity is correlated with the need for nucleotide precursors generated by the pentose phosphate pathway (PPP), of which G6PDH is the key enzyme. We suggest the synchronism of egg metabolism with carbohydrate distribution based on the decreasing levels of phosphoenolpyruvate carboxykinase (PEPCK) activity and on the elevation observed in protein content up to 24 HAE. Concomitantly, increasing levels of hexokinase (HK) and pyruvate kinase (PK) activity were observed, and PEPCK reached a peak around 48 HAE. Glycogen synthase kinase (GSK3) activity was also monitored and shown to be inversely correlated with glycogen distribution during embryogenesis.Conclusions: The results herein support the hypothesis that glucose metabolic fate changes according to developmental embryonic stages. Germ band retraction is a moment that was characterized as a landmark in glucose metabolism duringAedes aegyptiembryogenesis. Furthermore, the results also suggest a role for GSK3 in glycogen balance/distribution during morphological modifications.

Aqueous suspension of ethanol extracts of Derris (Lonchocarpus) urucu (Leguminosae), collected in the state of Amazonas, Brazil, were tested for larvicidal activity against the mosquito Aedes aegypti (Diptera:Culicidae). The aim of this study was to observe the alterations of peritrophic matrix in Ae. aegypti larvae treated with an aqueous suspension of D. urucu extract. Different concentrations of D. urucu root extract were tested against fourth instar larvae. One hundred percent mortality was observed at 150 microg/ml (LC(50) 17.6 microg/ml) 24 h following treatment. In response to D. urucu feeding, larvae excreted a large amount of amorphous feces, while control larvae did not produce feces during the assay period. Ultrastructural studies showed tha larvae fed with 150 microg/ml of D. urucu extract for 4 h have an imperfect peritrophic matrix and extensive damage of the midgut epithelium. Data indicate a protective role for the peritrophic matrix. The structural modification of the peritrophic matrix is intrinsically associated with larval mortality.

The Aedes aegypti mosquito is responsible for transmitting pathogens such as the Dengue, Zika, and Chikungunya viruses. The peritrophic matrix (PM) is an extracellular chitin-rich structure that lines the midgut of arthropods, providing a crucial protective barrier for the gut epithelium against mechanical damage, ingested pathogens, and toxic substances. During blood digestion, hemoglobin is lysed, releasing free heme into the midgut lumen. Part of this heme binds strongly to the PM, mitigating its harmful effects on the mosquito epithelial cells. Our study focused on investigating the interaction dynamic between hemoglobin and the PM during blood digestion in A. aegypti. Optical microscopy was employed to observe the temporal progression of blood digestion in the A. aegypti midgut, highlighting significant morphological changes in the blood bolus. An electrophoresis analysis revealed distinct protein bands in the PM extract, some of which were associated with hemoglobin and its subunits. The presence of PM-associated hemoglobin was confirmed by amino-terminal sequencing and an immunoblot analysis using anti-hemoglobin antibodies. Furthermore, fluorescence microscopy revealed overlapping labeling between hemoglobin and chitin, suggesting an interaction between hemoglobin and PM chitin. Corroborating these results, hemoglobin showed an affinity with chitin in the chromatography and molecular docking assays, in which the hemoglobin subunits interacted with the oligosaccharide (NAG)₄. Thus, hemoglobin may perform a function similar to that of peritrophins. Further experiments demonstrated the protective role of the PM against hemoglobin proteolysis during blood digestion. Overall, this study provides valuable insights into the intricate interactions between hemoglobin and the PM, enhancing our understanding of mosquito digestive physiology and potentially contributing to the development of vector control strategies.