Nitric oxide (NO) is a reactive gas that participates in many physiological as well as pathogenic processes in higher eukaryotic organisms. Inflammatory responses elicit higher levels of this molecule. Nevertheless, there are many technical challenges to accurately measure the amount of NO produced. Previously, a method using whole-cell extracts from Escherichia coli was able to generate the conversion of nitrate into nitrite to measure the amount of nitrate or indirectly the NO present in a sample using the Griess reaction. Here we present an improvement to this method, by using E. coli whole-cell extracts lacking one of the two nitrite reductases, rendered a more precise measurement when coupled with the Griess reaction than our previous report. Alternatively, osmotic stress showed to downregulate the expression of both nitrate reductases, which can be an alternative for indirect nitrate and NO reduction. The results presented here show an easy method for nitrate and NO reduction to nitrite and avoid the reconversion to nitrate, also as an alternative for other analytical methods that are based on cadmium, purified nitrate reductase enzyme, or salicylic methods to reduce NO. This method can be widely used for measuring NO production in living organisms, soil, and other relevant microbiological samples.

一氧化氮 (NO) 是一种反应性气体，参与高等真核生物的许多生理和致病过程。炎症反应会引发更高水平的这种分子。然而，准确测量产生的 NO 量存在许多技术挑战。以前，一种使用大肠杆菌全细胞提取物的方法能够将硝酸盐转化为亚硝酸盐，以使用 Griess 反应测量样品中硝酸盐的含量或间接测量 NO 的含量。在这里，我们提出了对这种方法的改进，通过使用缺乏两种亚硝酸盐还原酶之一的大肠杆菌全细胞提取物，与我们之前的报告相比，当与 Griess 反应结合时，可以提供更精确的测量。或者，渗透压显示下调两种硝酸盐还原酶的表达，这可以作为间接硝酸盐和 NO 还原的替代方法。此处显示的结果显示了一种将硝酸盐和 NO 还原为亚硝酸盐并避免再转化为硝酸盐的简单方法，还可作为其他基于镉、纯化硝酸盐还原酶或水杨酸方法来还原 NO 的分析方法的替代方法。该方法可广泛用于测量生物体、土壤和其他相关微生物样品中的 NO 产量。