The authors were interested in a mosquito gut commensal bacterium that promotes mosquito permissiveness to arboviruses. They found that the use of antibiotics to deplete the gut bacteria impaired arboviral infection of a lab-adapted Aedes aegypti mosquito strain. When individual cultivable gut bacteria were reconstituted in antibiotic-treated mosquitoes, the authors found that it was Serratia marcescens that is the commensal critical for efficient arboviral acquisition. S. marcescens was found to facilitate arboviral infection through a secreted protein, SmEnhancin, that digests membrane-bound mucins on the mosquito gut epithelia and enhances viral dissemination. Field Aedes mosquitoes that were infected with S. marcescens were found to be more permissive to dengue virus infection than those free of S. marcescens. The oral introduction of S. marcescens into field mosquitoes that lacked it also rendered the mosquitoes highly susceptible to arboviruses. Therefore the is a commensal-driven mechanism that contributes to vector competence in mosquitoes.
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