不同活性氧胁迫下Bacillus sp．F26以抗氧化物酶合成为特征的应激响应

Response of Bacillus sp.F26 to Different Reactive Oxygen Species Stress Characterized by Antioxidative Enzymes Synthesis

采用不同的活性氧发生源,研究了O_2^-·、H_2O_2和OH·胁迫下Bacillus sp.F26以抗氧化物酶合成为特征的应激响应。结果表明,细胞对氧胁迫的应激响应程度取决于活性氧种类、胁迫程度和形式(瞬时和持续)。Bacillus sp.F26对H_2O_2胁迫的响应程度最高,过氧化氢酶的快速合成对细胞抵抗H_2O_2胁迫至关重要,当细胞及时分解进入胞内的H_2O_2,胁迫对细胞的氧化损伤程度并不高,相反会刺激细胞的生长和底物消耗,当胁迫超过过氧化氢酶的分解能力时,H_2O_2会迅速抑制细胞生长和过氧化氢酶合成;由于O_2^-·与细胞作用的方式和效果与H_2O_2不同,超氧化物歧化酶和过氧化氢酶的快速合成并不能保证细胞及时有效地清除胞内的活性氧,因此,细胞对O_2^-·胁迫的响应程度要低于H_2O_2胁迫;在所考察的3种活性氧中,OH·胁迫(Fenton反应体系)对细胞的氧化损伤程度最大,胁迫强烈地抑制了细胞生长和抗氧化物酶的合成。由此表明,由于不同活性氧的化学性质有所不同,细胞对不同种类、程度和形式的活性氧胁迫会表现出不同的生物学效应,为了提高自身对氧胁迫的抵抗能力,微生物会通过自身的代谢调节适应新的环境,包括调整抗氧化物酶合成水平、改变生长速度以及底物消耗速率等。

The oxidative response of Bacillus sp F26 to different forms of reactive oxygen species （ROS） stress including H2O2, O2^- · and OH · were investigated by using diverse generating source of ROS, which were characterized by synthesis of antioxidative enzymes. It was shown that the responses of cells to oxidative stress are largely dependent on species, mode （instantaneous and continual） and intensity of stress. Higher synthesis rate of catalase （CAT） is crucial for Bacillus sp F26 to resist H2O2 stress. The damage of H2O2 to cell was minor if CAT can efficiently decompose H2O2 entering into cell, furthermore, the response can stimulate cell growths and sugar consumption. Conversely, cell growth and synthesis of antioxidative enzymes are greatly inhibited when the intensity of H2O2 stress overwhelms the cell capability of clearing H2O2. Due to the difference in mode and effect on cells between O2^- · and H2O2, higher synthesis rates of CAT and superoxide dismutase （SOD） couldn＇t guarantee cells to eliminate H2O2 and O2^- · efficiently. Therefore, the toxicity to cells induced by intracellular O2^- · is more severe than H2O2 stress. Unlike response to H2O2 and O2^- · , OH stress significantly inhibited cell growth and synthesis of antioxidative enzymes due to the fact OH · is most active ROS. Our results indicated that Bacillus sp F26 will show diverse biological behaviour in response to H2O2, O2^- · and OH · of stress due to the discrepancy in chemical property. In order to survive in oxidative stress, cells will timely adjust their metabolism to adapt to new environment including regulating synthesis level of antioxidative enzymes, changing rates of cells growth and substrate consumption.