棘孢木霉菌对钠胁迫的生理响应机制

Physiological response of Trichoderma asperellum to Na+ stress

摘要:

【背景】棘孢木霉菌制剂被广泛应用于生物防治和次生盐渍化土壤的微生物修复，但是关于棘孢木霉在盐渍化胁迫条件下生长的耐盐机理及其富集盐离子的能力尚缺乏深入研究。【目的】揭示一株耐盐棘孢木霉菌(Trichoderma asperellum) CTCCSJ-W-SBW10264 (T264)对钠胁迫的生理响应机制及其对钠离子的吸附和累积特性。【方法】设计梯度浓度钠胁迫培养实验，采集不同培养时期的菌丝样本，测定细胞氧化损伤相关指标H2O2和丙二醛(Malondialdehyde，MDA)的含量及细胞抗氧化相关酶的活性变化。【结果】钠胁迫实验表明，棘孢木霉T264能够在1.22 mol/L的钠胁迫环境中生存，在低于0.25 mol/L的钠胁迫下其生长不会被明显抑制。细胞氧化损伤及氧化损伤响应相关指标的研究结果表明，培养液中钠离子浓度越高，棘孢木霉的膜系统氧化水平(MDA含量)越高，而且随着细胞中MDA和H2O2的累积，细胞抵御氧化损伤相关酶的活性也有明显提高，在钠盐处理24 h后，0.5、1.0和1.22 mol/L的钠离子胁迫分别使过氧化物酶(Peroxidase，POD)、超氧化物歧化酶(Superoxide Dismutase，SOD)和过氧化氢酶(Catalase，CAT)活性达到峰值，依次为36.66、3.34和233.3 U/mg。钠离子吸附和累积特性实验结果表明，棘孢木霉T264的菌丝对钠离子有强的吸附能力。在0.05 mol/L的钠离子环境中培养72 h后，菌丝表面钠离子吸附量为1 347.6 mg/g，菌丝内部钠离子累积量为218.6 mg/g，木霉菌菌丝通过菌丝表面吸附和菌丝内部累积对培养液中钠离子的去除率达到32%。【结论】T264的抗氧化损伤相关酶在其耐受钠离子胁迫过程中发挥重要作用，菌株T264对高浓度钠离子有强适应性，而且对环境中钠离子有高效的吸附和累积作用。

Abstract:

[Background] Trichoderma asperellum agent has been widely used in biological control and secondary bioremediation of soil secondary salinization, while less is known about the salt-tolerant mechanism and salt accumulation potential of this strain under stress of salinization. [Objective] This research aimed to reveal the physiological response of Trichoderma asperellum CTCCSJ-W-SBW10264 (T264) to Na+-induced oxidative stress and the Na+ adsorption and accumulation characteristics of this strain. [Methods] Gradient concentrations of Na+ in broth were designed as stress factor in fermentation experiment of strain T264, then mycelia samples at different culture stages were collected for the measurement of cell oxidative damage indices including H2O2 content and malondialdehyde (MDA) level together with the activity of cellular antioxidant related enzymes. [Results] Result of Na+ stress cultivation experiment indicated that T264 could survive with Na+ concentration of 1.22 mol/L, and the growth of T264 was not significantly inhibited with Na+ concentration lower than 0.25 mol/L. The results of study on oxidative damage and oxidative damage responses revealed that the higher Na+ concentration lead to the higher cellular oxidation level (MDA content). Moreover, with the accumulation of MDA and H2O2 in hyphae of T264, the activity of antioxidative damage enzymes in cells was also increased significantly. After Na+ treatment for 24 h, the activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) were respectively highest under the Na+ stress of 0.5, 1.0 and 1.22 mol/L, respectively, which were 36.66, 3.34 and 233.3 U/mg. The experimental results of Na+ adsorption and accumulation characteristics showed that hyphae of T264 had a strong adsorption capacity for Na+. After being cultured in the 0.05 mol/L Na+ environment for 72 h, the surface Na+ adsorption capacity of mycelia was 1 347.6 mg/g, and the internal Na+ accumulation capacity of mycelia was 218.6 mg/g. The remove rate of Na+ in the culture medium reached 32% through surface adsorption and internal accumulation of T264 mycelia. [Conclusion] This experiment showed that the antioxidant damage-related enzymes of T264 play an important role in its resistance to Na+ stress, and the strain T264 has a strong adaptability to high concentration of Na+ and an efficient adsorption and accumulation effect of Na+ in the environment.