Escherichia coli alters the oviposition preference in Drosophila
LIU Wei1，2，*， ZHANG Ke1，3， LI En-Hui1，4， XU Hao-Zhe1，3， ZHANG Ce4
(1. Science and Technology Center， Shanxi Medical University Fenyang College， Fenyang， Shanxi 032200， China； 2. Department of Medical Laboratory Science， Shanxi Medical University Fenyang College， Fenyang， Shanxi 032200， China； 3. Department of Clinical Medical， Shanxi Medical University Fenyang College， Fenyang， Shanxi 032200， China； 4. Department of Physiology， Shanxi Medical University， Taiyuan 030001， China)
Abstract 【Aim】 This study aims to investigate the effects of the microbe Escherichia coli on the oviposition preference and survival rate of Drosophila melanogaster. 【Methods】 The 2-choice apparatus was used to examine the oviposition and position preference of wild-type D. melanogaster， and bacterial cells and supernatants were utilized to explore the reason for this behavior. D. melanogaster mutants of visual， gustatory and olfactory systems were applied to screen the corresponding sensing to E. coli， and the survival rates of pupae and adults of D. melanogaster were assessed to evaluate the potential effects of E. coli on oviposition selection. 【Results】 The female adults of D. melanogaster dramatically avoided to lay eggs on the fly diet fermented by E. coli， with an oviposition index of -0.89. The female adults avoided to oviposit on the supernatant of E. coli mixture， with an oviposition index of -0.52， but did not avoid to oviposit on the bacterial cells， with an oviposition index of 0.02. The Orco2 mutant was deficient in oviposition repellency to E. coli-associated diet with an oviposition index of -0.25. E. coli decreased the survival rate of D. melanogaster progeny， with less than 5% individuals surviving， and the scarification on food surface rescued the survival rate of pupae and adults of D. melanogaster. 【Conclusion】 Female adults of D. melanogaster select the E. coli fermented food as the favored oviposition site. The oviposition preference of flies stems from the metabolites rather than E. coli cells. The olfactory system is required for D. melanogaster to distinguish the favored oviposition site. The oviposition repellence to E. coli consequently increases the survival and adaption of their offspring， because E. coli forms the aquatic layer on food surface and deprives larvae of oxygen.