sodA、sodB和KatG在嗜水气单胞菌抗氧化胁迫中的协同作用

以嗜水气单胞菌野生株B11和基因稳定沉默株sodA-RNAi、sodB-RNAi和KatGRNAi为研究对象,比较野生株和沉默株在不同氧化胁迫条件下sodA,sodB和KatG表达的相关性及与细菌生长和存活的相关性,以探讨抗氧化胁迫基因在细菌抵御氧化胁迫过程中的作用和机制。结果显示,无氧化胁迫条件下sodA、sodB和KatG中任何一个基因被沉默后,其余两个基因的表达均受到显著抑制,说明这些抗氧化胁迫基因在表达上密切相关。在外源H2O2胁迫下,sodA、sodB和KatG中任何一个基因被沉默后,其他两个抗氧化胁迫基因的表达均表现为显著上调;在甲基紫晶(MV)诱导的内源性活性氧(ROS)胁迫下,各沉默株中sodA或sodB的表达水平总体表达为上调,但是在KatG的表达却呈现下调,说明sods的表达在细菌抵御内源性ROS的损伤中更具重要性。在H_2O_2胁迫下,随着H_2O_2浓度的增加,野生株B11的存活率仍然保持在较高的水平,而沉默株sodA-RNAi、sodB-RNAi和KatG-RNAi的存活率则显著降低;此外,菌株生长曲线显示,sodA、sodB和KatG的表达可影响嗜水气单胞菌生长曲线延滞期的长短。在不同浓度MV诱导的ROS胁迫下,野生株B11和沉默株KatG-RNAi的存活率仍然保持在较高的水平,沉默株sodA-RNAi和sodB-RNAi的存活率则显著降低,但4株菌仍然能保持一定的生长能力。研究表明,在不同氧化胁迫条件下,细菌可通过不同抗氧化胁迫基因的协同作用,共同抵御ROS的损伤,在H_2O_2的胁迫下,KatG对嗜水气单胞菌的生存更为重要,而在MV诱导的内源性ROS胁迫下,sod的表达对嗜水气单胞菌生存的贡献更为突出。

Synergism of sodA, sodB and KatG in Aeromonas hydrophila under antioxidative stress

To further explore the mechanism of Aeromonas hydrophila against oxidative stress, the correlations between the expressions of sodA, sodB and KatG in wild-type strain B11 and the gene silencing strains sodA-RNAi, sodB-RNAi and KatG-RNAi under different oxidative stresses were analyzed. Meanwhile, the correlation between the expressions of sodA, sodB and KatG and bacterial growth and survival was also studied. The results indicated that of the three genes (sodA, sodB and KatG), the silencing of any one gene resulted in significantly suppressed expression of the other two genes when they were under no oxidative stress. This indicated that these antioxidant stress genes were closely correlated in expression. Under H₂O₂ stress, silencing of one gene was always coupled with the significant up-regulation of the other two genes. Under MV-induced ROS stress, the expression of sodA andsodB genes in silencing strains was up-regulated, but the expression of KatG in strains sodA-RNAi and sodB-RNAi was down-regulated, indicating that the expression of two SODs genes was essential in resisting MV induced ROS damage. With the increase of H₂O₂ concentration, the survival rate of wild strain B11 remained at a high level, but the survival rate of gene silencing strains sodA-RNAi, sodB-RNAi and KatG-RNAi decreased significantly, and the expression of sodA, sodB and KatG was correlated with the length of the lag phase of A. hydrophila. Under different concentrations of MV stress, the survival rate of wild strain B11 and silencing strain KatG-RNAi remained at a relatively high level, while the survival rate of silencing strains sodA-RNAi and sodB-RNAi decreased significantly. But all the strains still maintained relatively good growth ability. These results suggested that under different oxidative stress conditions, bacteria can resist ROS damage through the synergism of different antioxidant stress genes. Under H₂O₂ stress, KatG is more important for the survival of A. hydrophila. Under MV-induced endogenous ROS stress, the expression of SODs genes contributes more to the survival of A. hydrophila.