共生菌通过氧气浓度调控果蝇产卵偏嗜性

Symbiotic bacteria regulate Drosophila oviposition preference by oxygen concentration

摘要:

[目的]研究东方醋杆菌（Acetobacter orientalis）和短小乳杆菌（Lactobacillus brevis）通过氧气浓度调控黑腹果蝇（Drosophila melanogaster）产卵的偏嗜性，并研究其对后代存活率和发育历期的生物学意义。[方法]利用双相选择装置解析果蝇产卵行为。利用分光光度仪和pH计测量细菌的OD值与pH值。通过改变果蝇的视觉、味觉和嗅觉感官以检测介导果蝇产卵行为的感觉系统。用后代的发育历期与存活率评价其生物学意义。[结果]果蝇产卵对东方醋杆菌具有趋避性，产卵指数为-0.76，对短小乳杆菌具有趋向性，产卵指数为0.5，并且二者接种比例决定了果蝇的产卵选择。氧气作为一个调节因子，可改变果蝇对东方醋杆菌和短小乳杆菌的产卵偏嗜性。氧气是东方醋杆菌生长必需的条件，有氧培养的OD值为1.3，而无氧培养的OD值为0.4。氧气是短小乳杆菌生长非必需的条件，有氧和无氧培养的OD值均为2.2。破坏嗅觉可严重地影响果蝇对细菌的产卵偏嗜性。东方醋杆菌和短小乳杆菌均促进了果蝇的生长，分别提高存活率1倍和1.5倍，分别缩短果蝇发育历期1 d和2 d。[结论]东方醋杆菌和短小乳杆菌可影响果蝇产卵偏嗜性，并且二者比例决定了果蝇的最终产卵选择。东方醋杆菌和短小乳杆菌通过感知氧气浓度的改变而进行不同的代谢方式，从而进一步调节果蝇产卵选择。嗅觉系统介导果蝇对东方醋杆菌和短小乳杆菌的产卵选择行为，从而提高后代存活率和缩短发育时间。

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.