摘要
快生大豆根瘤菌(Rhizobium fredii)RTl9在基本培养基中能耐800 mmol/L。NaCl。该菌株在对数生长后期,突然加入高浓度NaCl,使其培养液中的NaCl最终浓度为1000mmol/L。5分钟后,细胞内谷氨酸的含量便急剧增加,而且脯氨酸也大量积累。50分钟后,它们的含量分别达到未受盐激的(对照)4倍和3.8倍。在盐激条件下,RTl9的谷氨酰胺合成酶(GS)和谷氨酸合成酶(GOGAT)的活性比对照明显提高。其中GS活性的提高主要是由GSⅡ引起的,GSI变化不大。将这两种酶直接暴露于1000mmol/LNaCl,50分钟后,酶活性降至原来的70％,并未完全失活。聚丙烯酰胺凝胶双向电泳的分析表明,若干蛋白质在盐激后消失,而且发现两种蛋白质是新合成的,其分子量和等电点(MW/pI)分别为110 kD/4.3和76 kD/6.5。
Rhizobium fredii RT19 can grow in the presence of 800 mmol/L NaCl in the minimal medium. The intracellular levels of glutamate and proline were found to be elevated rapidly when high concentration of salt was added abruptly to the medium to a final concentration of 1000 mmol/L NaCl for 5 minutes. Fifty minutes after the salt shock, the intracellular concentration of glutamate and proline became 4-fold and 3. 8-fold of that in control cells, respectively. After salt shock, the activities of glutamine synthetase and glutamate synthase of RT19 were stimulated significantly in comparison with the control. In the case of GS, the activity of GS Ⅱ was stimulated, but not GS I . When the cell extracts were exposed to 1000 mmol/L NaCl for 50 minutes, the activities of these .enzymes were reduced and remained 70% of the control. The cell protein analysis by two-dimensional polyacrylamide gradient gel electrophoresis showed that some proteins were disappeared and two salt shock proteins were induced. One of these two proteins has a MW of 110kD and a pI of 4. 3, and the other has a MW of 76kD and a pI of 6. 5.
出处
《微生物学报》
CAS
CSCD
北大核心
1995年第1期1-6,共6页
Acta Microbiologica Sinica
基金
国家自然科学基金
关键词
盐激
大豆根瘤菌
渗透调节
根瘤菌
Salt shock, Fast-growing rhizobia, Osmoregulation
