Effects of Disruption of Homocitrate Synthase Genes on Nostoc sp. Strain PCC 7120 Photobiological Hydrogen Production and Nitrogenase
Effects of Disruption of Homocitrate Synthase Genes on Nostoc sp. Strain PCC 7120 Photobiological Hydrogen Production and Nitrogenase
复制标题
高柠檬酸合酶基因破坏对发菜的影响。
DOI：
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发表时间：
2007
影响因子：
4.4
通讯作者：
H. Sakurai
中科院分区：
文献类型：
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作者：
H. Masukawa;Kazuhito Inoue;H. Sakurai
摘要在以固氮酶为基础的蓝藻光生物制氢系统中，摄取氢酶（Hup）的失活导致产氢活性的显著增加。然而，在空气中，Hup突变体的高水平活性阶段仅持续几十小时，这种情况似乎是由活性固氮酶提供的足够量的结合氮引起的。固氮酶的催化性FeMo辅因子结合高柠檬酸，这是有效固氮所需的。先前报道了来自肺炎克雷伯氏菌的高柠檬酸合酶基因（nifV）破坏突变体的固氮酶在N2下显示出降低的固氮活性和增加的产氢活性。蓝细菌Nostoc sp.菌株PCC 7120具有两个高柠檬酸合酶基因nifV1和nifV2，以Nostoc sp.菌株PCC 7120的ΔhupL突变体为亲本菌株，构建了两个单突变体ΔhupL ΔnifV1（hupL和nifV1基因均被破坏）和ΔhupL ΔnifV2菌株，以及一个双突变体ΔhupL ΔnifV1 ΔnifV2菌株。两株nifV单突变株和双突变株的重氮营养生长速率分别比亲本ΔhupL菌株的重氮营养生长速率有中度和重度下降。ΔhupL ΔnifV1突变株的产氢活性在结合氮逐步降低约2 d后仍高于亲本ΔhupL菌株，且前者培养物中的产氢活性高于后者。N2气体的存在对ΔhupL ΔnifV1 ΔnifV2突变体产氢的抑制作用弱于亲本ΔhupL菌株以及ΔhupL ΔnifV1和ΔhupL ΔnifV2突变体。高柠檬酸合酶活性的改变可能是一个有用的策略，提高持续的光合产氢蓝藻。
ABSTRACT In the case of nitrogenase-based photobiological hydrogen production systems of cyanobacteria, the inactivation of uptake hydrogenase (Hup) leads to significant increases in hydrogen production activity. However, the high-level-activity stage of the Hup mutants lasts only a few tens of hours under air, a circumstance which seems to be caused by sufficient amounts of combined nitrogen supplied by active nitrogenase. The catalytic FeMo cofactor of nitrogenase binds homocitrate, which is required for efficient nitrogen fixation. It was reported previously that the nitrogenase from the homocitrate synthase gene (nifV) disruption mutant of Klebsiella pneumoniae shows decreased nitrogen fixation activity and increased hydrogen production activity under N2. The cyanobacterium Nostoc sp. strain PCC 7120 has two homocitrate synthase genes, nifV1 and nifV2, and with the ΔhupL variant of Nostoc sp. strain PCC 7120 as the parental strain, we have constructed two single mutants, the ΔhupL ΔnifV1 strain (with the hupL and nifV1 genes disrupted) and the ΔhupL ΔnifV2 strain, and a double mutant, the ΔhupL ΔnifV1 ΔnifV2 strain. Diazotrophic growth rates of the two nifV single mutants and the double mutant were decreased moderately and severely, respectively, compared with the rates of the parent ΔhupL strain. The hydrogen production activity of the ΔhupL ΔnifV1 mutant was sustained at higher levels than the activity of the parent ΔhupL strain after about 2 days of combined-nitrogen step down, and the activity in the culture of the former became higher than that in the culture of the latter. The presence of N2 gas inhibited hydrogen production in the ΔhupL ΔnifV1 ΔnifV2 mutant less strongly than in the parent ΔhupL strain and the ΔhupL ΔnifV1 and ΔhupL ΔnifV2 mutants. The alteration of homocitrate synthase activity can be a useful strategy for improving sustained photobiological hydrogen production in cyanobacteria.
影响因子：
2.9
作者：
LIANG, JH;MADDEN, M;BURRIS, RH
通讯作者：
BURRIS, RH