The physiological and biochemical effects of an allelochemical ethyl 2-methyl acetoacetate (EMA) isolated from reed (Phragmites communis) on bloom-forming cyanobacterium, Microcystis aeruginosa, were investigated. EMA significantly inhibited the growth of M. aeruginosa in a concentration-dependent way. The metabolic indices (represented by esterase and total dehydrogenase activities), the cellular redox status (represented by the level of reactive oxygen species (ROS)), and the oxidative damage index (represented by the content of malondialdehyde (MDA), the product of membrane lipid peroxidation) were used to evaluate the physiological and biochemical changes in M. aeruginosa after EMA exposure. Esterase activity in M. aeruginosa did not change (P>0.05) after 2 h of exposure to EMA, but increased greatly after 24 and 48 h (P<0.05). EMA exposure (>0.5 mg L(-1)) resulted in a remarkable loss of total dehydrogenase activity in M. aeruginosa after 4 h (P<0.01), but an increase after 40 h (P<0.05). EMA caused a great increase in ROS level of the algal cells. At high EMA concentration (4 mg L(-1)), the ROS level was remarkably elevated to 1.91 times as much as that in the controls after 2 h. Increases in the ROS level also occurred after 24 and 48 h. The increase in lipid peroxidation of M. aeruginosa was dependent upon EMA concentration and the exposure time. After 40 h of exposure, the MDA content at 4 mg L(-1) of EMA reached approximately 3.5 times (P<0.01) versus the controls. These results suggest that the cellular structure and metabolic activity of M. aeruginosa are influenced by EMA; the increased metabolic activity perhaps reflects the fact that the resistance of cellular response system to the stress from EMA is initiated during EMA exposure, and the oxidative damage induced by EMA via the oxidation of ROS may be an important factor responsible for the inhibition of EMA on the growth of M. aeruginosa.

中文翻译：

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化感化学2-乙酰乙酸乙酯（EMA）对铜绿微囊藻的生理和生化影响。

研究了从芦苇（芦苇）中分离出的化感化学物质2-甲基乙酰乙酸乙酯（EMA）对形成水华的蓝细菌铜绿微囊藻的影响。EMA以浓度依赖性方式显着抑制铜绿假单胞菌的生长。代谢指数（由酯酶和总脱氢酶活性表示），细胞氧化还原状态（由活性氧水平（ROS）表示）和氧化损伤指数（由丙二醛（MDA）含量表示）膜脂质过氧化反应）用于评估EMA暴露后铜绿假单胞菌的生理和生化变化。暴露于EMA 2小时后，铜绿假单胞菌的酯酶活性没有变化（P> 0.05），但在24和48 h后大大增加（P <0.05）。EMA暴露（> 0.5 mg L（-1））导致4 h后铜绿分支杆菌的总脱氢酶活性显着下降（P <0.01），但40 h后增加（P <0.05）。EMA导致藻类细胞的ROS水平大大提高。在高EMA浓度（4 mg L（-1））下，2小时后ROS水平显着提高至对照的1.91倍。24小时和48小时后，ROS水平也升高。铜绿假单胞菌脂质过氧化的增加取决于EMA浓度和暴露时间。暴露40小时后，相对于对照，在4 mg L（-1）EMA处的MDA含量达到约3.5倍（P <0.01）。这些结果表明，铜绿假单胞菌的细胞结构和代谢活性受EMA的影响。