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<p><i>Klebsiella oxytoca</i> is a N<sub>2</sub>-fixing bacterium whose <i>nif</i> (<i>ni</i>trogen <i>f</i>ixation) gene expression is controlled by the two antagonistic regulatory proteins NifA and NifL encoded by the <i>nifLA</i> operon. NifA is a transcriptional activator, while NifL inhibits the transcriptional activity of NifA. In order to develop an improved <i>K. oxytoca</i> strain with high N<sub>2</sub>-fixation efficiency, ammonium-excretion and plant-growth promotion, the negative regulatory gene <i>nifL</i> was deleted and accompanied by insertion of a constitutive Tc promoter upstream of the positive regulatory gene <i>nifA</i>. Engineered strain (designated as <i>K. oxytoca</i> TcP15) exhibited high nitrogenase activity and increased ammonium-excretion, both in the absence and presence of different NH<sub>4</sub><sup>+</sup> concentrations. Greenhouse experiments showed that engineered <i>K. oxytoca</i> TcP15 promoted growth of cucumber, tomato and rice more efficiently than wild-type <i>K. oxytoca</i> M5al did. This study demonstrates that engineered <i>K. oxytoca</i> TcP15 has the potential to be utilized as biofertilizer for non-legumes in nitrogen-poor and -rich fields.</p>

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Modification of nifL-nifA operon of Klebsiella oxytoca improves N2-fixation efficiency, ammonium-excretion and plant-growth promotion ability

  • 期刊论文

  • 发表日期：

    2025年9月8日

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  • Peichun Lan,
  • Yimin Shang,
  • Shuo Jiao,
  • Gehong Wei,
  • Ruizong Jia,
  • Wanbin Zhu,
  • Sanfeng Chen

摘要

Klebsiella oxytoca is a N2-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 N2-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 NH4+ 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.