摘要
弗雷德中华根瘤菌(Sinorhizobium fredii)RT19是快生型大豆根瘤菌。该菌株在不同浓度 NaCl 条件下,其细胞内的游离谷氨酸和钾离子含量随盐浓度的提高而急剧增加。在无盐和低浓度 NaCl 条件下,测不出细胞内有游离苏氨酸,但在较高浓度盐存在时,其含量也随着盐浓度的提高而递增。RT19在对数生长后期,突然加入 NaCl,使其培养液中的 NaCl 的最终浓度达到300mmol/L,定时取样测定细胞内氨基酸含量,发现5分钟后谷氨酸含量急剧上升,比不加盐的对照高出5倍,而且在3小时内保持不变.苏氨酸也出现类似情况。测定了 RT19及其转化子 RTt19和 RTt50的谷氨酸脱氢酶(GDH)、谷氨酰胺合成酶(GS)和谷氨酸合成酶(GOGAT)在盐压下的活性,发现在300 mmol/L NaCl 或300mmol/L KC1存在时,GDH 酶活性稍为下降或不变,而 GS 和 GOGAT 酶活性则显著提高。
S.fredii RT19 is a fast-growing soybean rhizobium strain.In the presence of differentconcentrations of NaCl,intracellular levels of K^+ and free glutamate were elevated rapidlywith increasing the salt concentration.It is interesting that the threonine was not detected wi-thout NaCl or at low concentrations of NaCI,whereas its level was enhanced in response toincteasing the NaCl concentration.The intracellular glutamate levels increased immediately when salt was added suddenly toculture to a final concentration of 300mmol/L NaCl.The intracellular glutamate concentra-tion became 6-fold of that in the control cells in 5 minutes,and remained almost the same for3 hours.Similar changes were observed for threonine.The activity of glutamate dehydrogenase(GDH),glutamine synthetase(GS)and glurama-te synthase(GOGAT)of RT19 and its transformants RTt19 and RTt50 were assayed under saltstress.It was found that GS and GOGAT activities were stimulated significantly while GDHactivity slightly decreased or unaffected by 300 mmol/L NaCl or 300 mmol/L KCl.
出处
《微生物学报》
CAS
CSCD
北大核心
1993年第2期86-91,共6页
Acta Microbiologica Sinica
基金
国家自然科学基金
关键词
快生型
大豆根瘤菌
根瘤菌
调节
Fast-growing soybean rhizobia
Osmoregulation
Glutamate
