Abstract
BackgroundThe 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.ResultsThe 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.ConclusionsThe 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.
Highlights
The insect gut harbors a variety of microorganisms that probably exceed the number of cells in insects themselves
Their function in blood digestion has not been determined to date, it is well known that the bacterial population increases substantially after blood feeding
Effect of the reduction of midgut bacteria in the digestion of blood proteins In order to evaluate if reduction of midgut bacteria could interfere with blood protein digestion, mosquitoes were treated with different antibiotics, fed on mouse and the protein content per gut was measured at 24 h, 36 h and 48 h after blood feeding (ABF)
Summary
The insect gut harbors a variety of microorganisms that probably exceed the number of cells in insects themselves. Insects host many microorganisms that colonize and grow inside their tissues, mainly in the digestive system These microbes are involved in various physiological functions, including food digestion, nutrition, nitrogen fixation and reproduction. A previous study [7] proposed that bacteria present in Aedes aegypti gut ventral diverticulum could play a role in sugar metabolism processes. Their function in blood digestion has not been determined to date, it is well known that the bacterial population increases substantially after blood feeding (ABF) [4,5,9], suggesting a potential contribution to digestive process as observed in other insects [12]
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