摘要
通过三亲本杂交将质粒 pCK3[携带改变了启动子的肺炎克氏杆菌(Klebsiella pneumoniae)nifA 基因]引入巴西固氮螺菌(Azospirillum brasilense)Yu62菌株中,由此获得的转移接合子巴西固氮螺菌 Yu62-4菌株在6.0 mmol/L 以上 NH^+_4浓度下,能表现出微弱的固氮酶活性(相当于无 NH^+_4时活性的0.3—0.5%),而野生型 Yu62则全部丧失固氮酶活性。固氮酶的丙烯酰胺凝胶电泳和铁蛋白的免疫杂交实验表明,转移接合子 Yu62-4在高 NH^+_4(50mmol/L)下,虽有铁蛋白合成,但合成量比无 NH^+_4时少得多,而且有一部分铁蛋白未被共价修饰;野生型菌株 Yu62在此 NH^+_4浓度下无铁蛋白合成。实验结果表明:外源(来自肺炎克。’氏杆菌)的基因产物在巴西固氮螺菌 Yu62中不能有效地解除 NH^+_4对该菌固氮酶合成的阻遏作用。本文分析了出现这种现象的原因。
with the triparental mating,the pCK3plasmid,which carried the nifA gene of Kle-bsiella pneumoniae and its modified promoter,was transfered into Azospirillum brasilenseYu62 and it was stable.When the ammoniaconcentration was higher than 6.0mmol/L,the transconjugant Yu62—4 had a little acti-vity of nitrogenase which was 0.3—0.5% ofthat in the absence of ammonia,but wild typeYu62 had no any nitrogenase actvity at thesame concentration.SDS-PAGE of MoFe pro-tein and Western Blotting of Fe protein show-ed that Yu62-4 had synthesized Fe protein at50mmol/L NH_4^+ and its amount was less thanthat of Yu62 at 0mmol/L NH_4^+ and part ofFe protein was not covalently modified.Wildtype Yu62 had not synthesized Fe protein at10mmol/L NH_4^+.The result showed that thenifA gene product of K.pneumoniae couldnot effectively break down the repression ofnitrogenase synthesis by ammonia in A.brasi-lense Yu62.
出处
《微生物学报》
CAS
CSCD
北大核心
1991年第5期338-345,共8页
Acta Microbiologica Sinica
基金
国家自然科学基金
关键词
巴西固氮螺菌
固氮基因
功能
Azospirillum brasilense
Role of foreign nifA
