Symbiotic bacteria regulate Drosophila oviposition preference by oxygen concentration

Abstract:

[Objective] We studied how Acetobacter orientalis and Lactobacillus brevis regulate the oviposition preference of Drosophila melanogaster by oxygen concentration and further explored the biological significance of this phenomenon through the survival rate and developmental duration of offspring. [Methods] The egg-laying behavior of Drosophila melanogaster was analyzed by using a double selection device. The OD value and pH value of bacteria were measured by spectrophotometer and pH meter. The system that mediates the oviposition preference of Drosophila was detected by altering the visual, taste and olfactory senses of Drosophila. The biological significance was evaluated by the developmental duration and survival rate of offspring.[Results] Drosophila melanogaster tended to avoid laying egg on the side of Acetobacter orientalis, the oviposition index was -0.76, but liked to lay egg on the side of Lactobacillus brevis, and the oviposition Index was 0.5, the ratio of the two bacteria determined the oviposition selection of Drosophila melanogaster. Anaerobic environment reversed the oviposition preference to Acetobacter orientalis and Lactobacillus brevis. The OD value of Acetobacter orientalis was 1.3 in aerobic environment but 0.4 in anaerobic environment. The OD value of Lactobacillus brevis was 2.2 in both aerobic and anaerobic environment. Disrupting the sense of smell affected the Drosophila's oviposition to bacteria. Both Acetobacter orientalis and Lactobacillus brevis promoted the growth of Drosophila under anaerobic and aerobic environment, increased the survival rate by 1 and 1.5 times respectively, and shortened the development period of Drosophila by 1 and 2 days respectively. [Conclusion] Both Acetobacter orientalis and Lactobacillus brevis affected the oviposition preference of Drosophila, and the ratio of them determined the final oviposition selection. Acetobacter orientalis and Lactobacillus brevis had different metabolic modes by sensing the change of oxygen, and further regulated the oviposition preference of Drosophila. Olfactory system mediated the oviposition selection behavior of Drosophila melanogaster. Both Acetobacter orientalis and Lactobacillus brevis improved the survival rate of offspring and shorten the development duration.