Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai'i at Manoa, Honolulu, Hawai'i, USA.
J Phycol. 2021 Jun;57(3):863-873. doi: 10.1111/jpy.13129. Epub 2021 Apr 13.
The production of dihydrogen (H ) is an enigmatic yet obligate component of biological dinitrogen (N ) fixation. This study investigates the effect on H production by N fixing cyanobacteria when they are exposed to either air or a gas mixture consisting of argon, oxygen, and carbon dioxide (Ar:O :CO ). In the absence of N , nitrogenase diverts the flow of electrons to the production of H , which becomes a measure of Total Nitrogenase Activity (TNA). This method of argon-induced hydrogen production (AIHP) is much less commonly used to infer rates of N fixation than the acetylene reduction (AR) assay. We provide here a full evaluation of the AIHP method and demonstrate its ability to achieve high-resolution measurements of TNA in a gas exchange flow-through system. Complete diel profiles of H production were obtained for N fixing cyanobacteria despite the absence of N that broadly reproduced the temporal patterns observed by the AR assay. Comparison of H production under air versus Ar:O :CO revealed the efficiency of electron usage during N fixation and place these findings in the broader context of cell metabolism. Ultimately, AIHP is demonstrated to be a viable alternative to the AR assay with several additional merits that provide an insight into cell physiology and promise for successful field application.
氢气（H ）的产生是生物固氮（N ）固定过程中一个神秘但必需的组成部分。本研究探讨了当固氮蓝藻暴露于空气或由氩气、氧气和二氧化碳（Ar:O :CO ）组成的混合气体中时，对 H 产生的影响。在没有 N 的情况下，固氮酶会将电子流转移到 H 的产生上，这成为总氮酶活性（TNA）的衡量标准。与乙炔还原（AR）测定法相比，这种氩诱导产氢（AIHP）方法较少用于推断 N 固定的速率。我们在这里全面评估了 AIHP 方法，并证明了它在气体交换流动系统中实现 TNA 高分辨率测量的能力。尽管缺乏 N ，但仍获得了固氮蓝藻 H 产生的完整昼夜曲线，这些曲线广泛再现了 AR 测定法观察到的时间模式。在空气和 Ar:O :CO 下的 H 产生比较揭示了 N 固定过程中电子使用的效率，并将这些发现置于细胞代谢的更广泛背景下。最终，AIHP 被证明是 AR 测定法的可行替代方法，具有几个额外的优点，可以深入了解细胞生理学，并有望在野外成功应用。
