Vin­cent, Elio, Michael, and Michele con­sider whether our eat­ing be­hav­ior is ma­nip­u­lated by gas­troin­testi­nal mi­cro­biota, and an aphid gene of bac­te­r­ial ori­gin whose gene prod­uct en­codes a pro­tein that is trans­ported to an ob­lig­ate en­dosym­biont.