短小乳杆菌的代谢产物对黑腹果蝇产卵选择性的影响

【目的】研究黑腹果蝇Drosophila melanogaster对短小乳杆菌Lactobacillus brevis有氧与无氧代谢产物的产卵选择，并解析这些代谢产物影响果蝇产卵行为的机制和生物学意义。【方法】应用产卵双选择装置，检测成年雌果蝇产卵的选择行为；利用黑暗条件(暗盒)、嗅觉突变体和摘除前足味觉感受器的方式探究介导该行为的感觉系统；通过在不同浓度乳酸(0, 70, 280 mmol/L)的培养基上培养黑腹果蝇，探究乳酸对其后代的发育历期和存活率的影响；利用免疫荧光染色法检测乳酸对果蝇肠道上皮细胞增殖情况的影响。【结果】短小乳杆菌无氧代谢产物引起成年雌性黑腹果蝇产卵避性，产卵指数为-0.47；短小乳杆菌有氧代谢产物乳酸含量为0.4 mmol/L，无氧代谢产物乳酸含量为126.8 mmol/L；雌性果蝇对乳酸同样产生产卵避性反应，且产卵避性随乳酸浓度的增高而增强。切除前足的果蝇对乳酸的产卵避性显著降低。与对照相比， 70 mmol/L的乳酸使幼虫的成蛹时间和成虫羽化时间分别延长了1.42 d和1.17 d，存活率降低了36.0%。乳酸明显破坏肠道上皮的完整性，促进肠道上皮细胞的增殖。【结论】短小乳杆菌无氧代谢产物引起成年果蝇产卵避性。果蝇主要通过味觉感知短小乳杆菌无氧代谢产物乳酸，这引起果蝇产卵避性，从而提高后代的生长发育和幼虫的存活率。

Effects of the metabolites ofLactobacillus brevison the oviposition selection ofDrosophila melanogaster

【Aim】 This study aims to investigate the oviposition selection of Drosophila melanogaster to aerobic and anaerobic metabolites of Lactobacillus brevis, and to elucidate the underlying mechanism and biological significance of their effects on Drosophila oviposition behavior. 【Methods】 The oviposition preference of female adults of D. melanogaster was assayed by using the two-choice apparatus. The sensory modality that mediates this behavior was studied by using dark conditions, olfactory mutants and flies with forelegs surgically removed. The developmental duration and survival rate of offspring were determined to evaluate the biological significance of the oviposition avoidance to lactic acid. The intestinal epithelial cell proliferation was observed by immunofluorescence. 【Results】 The female adults of D. melanogaster avoided laying eggs on food covered with metabolites of L. brevis by anaerobic fermentation, with the oviposition index of -0.47. The concentration of the metabolite lactic acid was 0.4 mmol/L under the aerobic condition, while it was 126.8 mmol/L under the anaerobic condition. Female adults of D. melanogaster avoided laying eggs on the food with lactic acid, and the oviposition index decreased with lactic acid in a dosage dependent manner. D. melanogaster had obvious oviposition avoidance to lactic acid. The oviposition avoidance response was impaired in the flies with forelegs surgically removed. The time to puparium formation and to adult emergence of the larvae on the food with 70 mmol/L lactic acid was prolonged by 1.42 d and 1.17 d, respectively, and the larval survival rate decreased by 36.0%, as compared to those of the control. Lactic acid induced intestinal dysplasia with the increased number of mitotic cells. 【Conclusion】 Female adults of D. melanogaster avoid laying eggs on the food covered with metabolites of L. brevis by anaerobic fermentation. The metabolite lactic acid produced under anaerobic condition, which is detected by flies mainly through taste perception, induces the oviposition avoidance of D. melanogaster, thus promoting the development and the survival rate of their progeny.