短期高温伤害蓝藻Anabaena7120的固氮活性恢复与生理条件的关系

Relationship Between the Recovery of Nitrogenase Activity of Blue-Green Algae Anabaena 7120 Injured by Short high Temperature Treatment and Physiological Conditions

蓝藻经短期高温处理后,其固氮活性显著下降,但在合宜条件下,这种受伤害的固氮活性可以有一定程度的恢复。光下不仅比暗中恢复快,而且活性也高得多。光合抑制剂和外源碳水化合物分别减缓和促进受高温伤害的蓝藻固氮活性恢复。在光、暗和供给外源碳水化合物的条件下,厌氧(氩和氮中)对受高温伤害的蓝藻固氮活性恢复不利。与正常蓝藻有异的是,H_2,CO_2及H_2与O_2,CO_2与N_2的加合都阻碍受高温伤害的蓝藻固氮活性的恢复。

The paper deals with the effects of several physiological conditions on the recovery of nitrogenase activity in Anabaena 7120 injured by high temperature in short time. Anabaena 7120 was grown in Allen-Arnon medium with molecular nitrogen as nitrogen source. Culture conditions were the same as described previously (Chen and Fang 1983). Cells were harvested in logarithmic growth phase (usually after 3～5 days of culture) and concentrated by sedimentation to a final OD (1 cm, 650 nm)of 0.8～1. 2. Cell suspensions were put into 10 ml incubation vessels. Algal suspensions were treated at 45℃ in water bath for 1 min, and then incubated under different physiological conditions in light at 30℃ for 20 h. After that the nitrogenase activity of cells was determined. At first the vessels were filled with pure argon, and then 10% C_2H_2 (V/V) were added and allowed to react under shaking in light a 30℃. Ethylene was determined by gas chromatography with flame ionization detector after different time intervals. It was shown that nitrogenase activity of Anabaena treated with short high temperature treatment decreased with an increase of temperature. Under appropriate conditions the nitrogenase activity suppressed by high temperature could be restored. depending on the temperature and time of treatment. The recovery of nitrogenase activity of Anabaena injured by high temperature for a short time varied with the physiological condition. The acetylene reduction activity of Anabaena injured by high temperature recovered more rapidly in light than in the dark. Photosynthetic inhibitors, such as DNP and CCCP, prevented the recovery of nitrogenase activity of Anabaena injured by high temperature, while sucrose accelerated it, either in light or in the dark, or in the presence of external sucrose. The recovery of nitrogenase activity of Anabaena in jured by high temperature was slower and to a lesser degree under anaerobic condition (in Ar or N_2) than that under aerobic condition. The addition of H_2 or CO_2, H_2 and O_2 or CO_2 and N_2 could promote the C_2H_2-reduction activity of normal alga cells, but had no effect on the recovery of C_2H_2-re duction activity in Anabaena injured by high temperature for a short time. The mechanism of the recovery of nitrogenase activity of Anabaena 7120 injured by short high temperature treatment was discussed.