蓝藻Anabaena 7120光漂白细胞固氮的研究

蓝藻Anabaena 7120经光漂白后固氮活性明显下降,转入正常光照下又恢复活性。此种经光漂白的蓝藻细胞,其固氮活性对氧敏感度小,受分子氢的促进大些,而忍受CO_2和N_2抑制的浓度相对高些。其固氮活性为弱光和光合抑制剂减弱,而加入外源的碳水化合物则能提高它的固氮活性。当碳水化合物和光合抑制剂一起加入反应系统时,蓝藻光漂白细胞的固氮活性并不能受到促进。

STUDY ON NITROGEN FIXATION BY PHOTOBLEACHED FILAMENTS OF BLUE-GREEN ALGAE ANABAENA 7120

We have studied the nitrogen fixation by photobleached cells of the hetero-cystous blue-green algae Anabaena 7120. We found that the photobleached cellsbecame pale green-yellow after 24 hours and the yellow filaments reduced muchless C_2H_2 than normal green ones (Fig. 1). Under normal growth conditions, theC_2H_2-reducing activity of Anabaena cells suppressed by photobleaching was restored(Fig. 1) and cells became blue-green again, too. The characteristics of nitrogen fixation in photobleached Anabaena cells vary,depending upon the physiological condition. It has been observed that: (1) C_2H_2-reducing activity in photobleached cells was less sensitive to oxygen than in normalones (Fig. 2). (2) The H_2-supported nitrogenase activity in photobleached cellswas higher than that in normal cells (Table 1). (3) The suppression of nitrogenaseactivity by CO_2 and N_2 in normal cells of algae was higher than that in the photo-bleached cells (Fig. 3, 4). Weak light and photosynthesis inhibitors suppressed nitrogenase activity inphotobleached cells. The addition of glucose, sucrose, mannitol, pyruvate orglucose-6-phosphate to test systems had enhancing effect on the. C_2H_2-reducingactivity in photobleached cells. But no enhancing effect was observed When any ofthe carbonhydrates was added simultaneously with photosynthesis inhibitors(Fig. 5, Table 2,3). The mechanism of nitrogen fixation and interrelationship between nitrogenfixation and photosynthesis in photobleached cells of Anabaena 7120 have beensuggested.