Lan Peichun, Shang Yimin, Jiao Shuo, Wei Gehong, Jia Ruizong, Zhu Wanbin, Chen Sanfeng
College of Biological Sciences, China Agricultural University, Beijing, 100193, China.
State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Life Sciences, Northwest A&F University, Yangling, 712100, Shaanxi, China.
Arch Microbiol. 2025 Sep 8;207(10):253. doi: 10.1007/s00203-025-04457-2.
Klebsiella oxytoca is a N-fixing bacterium whose nif (nitrogen fixation) gene expression is controlled by the two antagonistic regulatory proteins NifA and NifL encoded by the nifLA operon. NifA is a transcriptional activator, while NifL inhibits the transcriptional activity of NifA. In order to develop an improved K. oxytoca strain with high N-fixation efficiency, ammonium-excretion and plant-growth promotion, the negative regulatory gene nifL was deleted and accompanied by insertion of a constitutive Tc promoter upstream of the positive regulatory gene nifA. Engineered strain (designated as K. oxytoca TcP15) exhibited high nitrogenase activity and increased ammonium-excretion, both in the absence and presence of different NH concentrations. Greenhouse experiments showed that engineered K. oxytoca TcP15 promoted growth of cucumber, tomato and rice more efficiently than wild-type K. oxytoca M5al did. This study demonstrates that engineered K. oxytoca TcP15 has the potential to be utilized as biofertilizer for non-legumes in nitrogen-poor and -rich fields.
产酸克雷伯菌是一种固氮细菌，其固氮（nif）基因的表达受nifLA操纵子编码的两种拮抗调节蛋白NifA和NifL的控制。NifA是一种转录激活因子，而NifL抑制NifA的转录活性。为了培育出一种固氮效率高、铵排泄量高且能促进植物生长的改良产酸克雷伯菌菌株，删除了负调控基因nifL，并在正调控基因nifA上游插入了一个组成型Tc启动子。工程菌株（命名为产酸克雷伯菌TcP15）在不同NH浓度存在和不存在的情况下均表现出高固氮酶活性和增加的铵排泄量。温室实验表明，工程产酸克雷伯菌TcP15比野生型产酸克雷伯菌M5al更有效地促进了黄瓜、番茄和水稻的生长。这项研究表明，工程产酸克雷伯菌TcP15有潜力在贫氮和富氮田地中用作非豆科植物的生物肥料。
