• 作者： 劉仲康; 劉家漢; 林全信
• 作者服務機構： 國立中山大學生命科學所; 國立中山大學海洋資源學系
• 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1mM氰化鉀與5mM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善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, cya-nide can also serve as a subtrate for nitrogenase and can be reduced to CH4 and NH4+. A cyanide-degradingKlebsiella oxytoca strain was isolated from cyanide contaminated water. This isolate was also found to havea 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 foundthat the cyanide-degrading ability of this isolate could be inhibited by multicopy hybrid pGR112 nif-con-taining plasmids. Comparing the wild type K. oxytoca strain with the pGR112 plasmid transformed strain,a typical diauxic growth of the wild type strain was observed in a medium containing NH4Cl and KCN. Al-though the nif plasmid transformed strain also exhibited diauxic growth in the same medium, a much longersecond lag phase was noted. In addition, methane, the nitrogenase reduction end product of cyanide, could bedetected on cyanide-containing growth cultures. Ammonium chloride, a repressor of nitrogenase gene ex-pression, was consumed prior to KCN in both strains. Again, the degradation of KCN in the pGR112 trans-formed strain occurred only under loose control of the nitrogenase gene. These findings strongly suggest thatnitrogenase may be the sole cyanide-degrading enzyme in this organism.
• 中文關鍵字： cyanide; nitrogenase; Klebsiella oxytoca.
• 英文關鍵字： --