頁籤選單縮合
題 名 | The Role of Nitrogenase in a Cyanide-Degrading Klebsiella Oxytoca Strain=固氮酵素在一株氰化物分解菌Klebsiella Oxytoca中扮演的角色 |
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作 者 | 劉仲康; 劉家漢; 林全信; | 書刊名 | Proceedings of the National Science Council : Part B, Life Science |
卷 期 | 21:2 1997.04[民86.04] |
頁 次 | 頁37-42 |
分類號 | 361.4 |
關鍵詞 | 固氮酵素; 氰化物分解菌; Cyanide; Nitrogenase; Klebsiella oxytoca; |
語 文 | 英文(English) |
中文摘要 | 眾所周知,固氮酵素的主要功能為固定大氣中的氮氣。然而,氰化物也可作為固 氮酵素的受質,並被還原成甲烷與氨。我們自氰化物污染水域中分離出一株能分解氰化物的 Klebsiella oxytoca 細菌,並發現此菌株亦具有固氮功能。 氰化鉀可誘發此菌的固氮活性 ,但是 1 mM 氰化鉀與 5 mM 氰化鉀的誘導效應並無顯著差異。此菌的氰分解能力會被一含 有固氮酵素基因的 pGR112 質體所抑制。在比較野生型 K. oxytoca 菌株及以 pGR112 質體 轉形之突變菌株的生長情形後發現,於含有氯化銨及氰化鉀的培養基中,野生型菌株會呈現 出典型的雙週期生長方式( diauxic growth )。雖然含固氮基因質體的突變株在相同培養 基中也呈現出雙週期的生長,但其生長遲滯期則顯著較長。此外,固氮酵素分解氰化物的產 物-甲烷,也可自含氰培養的菌液中發現。氯化銨是固氮基因表現的抑制劑,於含有氰化鉀 的培養液中,不論是野生菌株或突變株,均優先使用氯化銨作為氮源;當氯化銨消耗殆盡解 除對固氮基因的抑制後,氰化鉀才能開始被吸收利用。而含 pGR112 質體的轉形株只能在固 氮酵素不嚴密關閉的情況下進行分解氰化鉀的作用。上述種種發現均強烈暗示此菌株的固氮 酵素亦是其唯一的氰化物分解酵素。 |
英文摘要 | It is well known that the major function of nitrogenase is to fix atmospheric nitrogen. However, cyanide can also serve as a subtrate for nitrogenase and can be reduced to CH �� and NH ����. A cyanide-degrading Klebsiella oxytoca strain was isolated from cyanide contaminated water. This isolate was also found to have a nitrogen-fixation capability. Nitrogenase activities in this organism could be induced by KCN. However, there was no significant difference of the induction effect between 1 mM KCN and 5 mM KCN. It was found that the cyanide-degrading ability of this isolate could be inhibited by multicopy hybrid pGR112 nif-containing plasmids. Comparing the wild type K. oxytoca strain with the pGR112 plasmid transfformed strain, a typical diauxic growth of the wild type strain was observed in a medium containing NH �� Cl and KCN. Although the nif plasmid transformed strain also exhibited diauxic growth in the same medium, a much longer second lag phase was noted. In addition, methane, the nitrogenase reduction end product of cyanide, could be detected on cyanide-containing growth cultures. Ammonium chloride, a repressor of nitrogenase gene expression, was consumed prior to KCN in both strains. Again, the degradation of KCN in the pGR112 transformed strain occurred only under loose control of the nitrogenase gene. These findings strongly suggest that nitrogenase may be the sole cyanide-degrading enzyme in this organism. |
本系統中英文摘要資訊取自各篇刊載內容。