Ushiki Norisuke, Jinno Masaru, Fujitani Hirotsugu, Suenaga Toshikazu, Terada Akihiko, Tsuneda Satoshi
Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
Department of Chemical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, Tokyo 184-8588, Japan.
J Biosci Bioeng. 2017 May;123(5):581-589. doi: 10.1016/j.jbiosc.2016.12.016. Epub 2017 Feb 13.
Nitrite oxidation is an aerobic process of the nitrogen cycle in natural ecosystems, and is performed by nitrite-oxidizing bacteria (NOB). Also, nitrite oxidation is a rate-limiting step of nitrogen removal in wastewater treatment plants (WWTPs). Although Nitrospira is known as dominant NOB in WWTPs, information on their physiological properties and kinetic parameters is limited. Here, we report the kinetic parameters and inhibition of nitrite oxidation by free ammonia in pure cultures of Nitrospira sp. strain ND1 and Nitrospira japonica strain NJ1, which were previously isolated from activated sludge in a WWTP. The maximum nitrite uptake rate ( [Formula: see text] ) and the half-saturation constant for nitrite uptake ( [Formula: see text] ) of strains ND1 and NJ1 were 45 ± 7 and 31 ± 5 (μmol NO/mg protein/h), and 6 ± 1 and 10 ± 2 (μM NO), respectively. The [Formula: see text] and [Formula: see text] of two strains indicated that they adapt to low-nitrite-concentration environments like activated sludge. The half-saturation constants for oxygen uptake ( [Formula: see text] ) of the two strains were 4.0±2.5 and 2.6±1.1 (μM O), respectively. The [Formula: see text] values of the two strains were lower than those of other NOB, suggesting that Nitrospira in activated sludge could oxidize nitrite in the hypoxic environments often found in the interiors of biofilms and flocs. The inhibition thresholds of the two strains by free ammonia were 0.85 and 4.3 (mg-NH l), respectively. Comparing the physiological properties of the two strains, we suggest that tolerance for free ammonia determines competition and partitioning into ecological niches among Nitrospira populations.
亚硝酸盐氧化是自然生态系统中氮循环的一个需氧过程，由亚硝酸盐氧化细菌（NOB）进行。此外，亚硝酸盐氧化是污水处理厂（WWTPs）中氮去除的限速步骤。尽管硝化螺菌属被认为是污水处理厂中占主导地位的NOB，但关于它们生理特性和动力学参数的信息有限。在此，我们报告了从污水处理厂活性污泥中分离出的硝化螺菌属菌株ND1和日本硝化螺菌菌株NJ1纯培养物中亚硝酸盐氧化的动力学参数以及游离氨对其的抑制作用。菌株ND1和NJ1的最大亚硝酸盐摄取速率（[公式：见正文]）和亚硝酸盐摄取的半饱和常数（[公式：见正文]）分别为45±7和31±5（μmol NO/毫克蛋白质/小时），以及6±1和10±2（μM NO）。两种菌株的[公式：见正文]和[公式：见正文]表明它们适应活性污泥等低亚硝酸盐浓度环境。两种菌株的氧气摄取半饱和常数（[公式：见正文]）分别为4.0±2.5和2.6±1.1（μM O）。两种菌株的[公式：见正文]值低于其他NOB，这表明活性污泥中的硝化螺菌可以在生物膜和絮体内部常见的缺氧环境中氧化亚硝酸盐。两种菌株对游离氨的抑制阈值分别为0.85和4.3（mg-NH l）。比较两种菌株的生理特性，我们认为对游离氨的耐受性决定了硝化螺菌种群之间在生态位中的竞争和分布。
