Abstract The controversial arguments on the true substrate in nitritation kinetics might be due to the cells' dual substrate-transport system. Our experiments revealed that, under ammonia-rich environments, it diffused into the membrane (ammonia was the direct substrate); but, under oligotrophic, ammonium ion was actively transported (ammonium was the direct substrate). Facilitating this change-over, the bacterial composition in the sludge was altered, although the predominant was Nitrosomonas eutropha in most of the six chemostats. Also, the substrate affinity constant (Ks) fell resulting in partial compensation for the reduced availability of substrate. When the environmental ammonia concentration was lower than the cytoplasmic one, a backward diffusion appeared to take place, which probably had the cells accelerate its energy-consuming ammonium transport. The % ammonium oxidizing bacteria (AOB) to the total number of bacteria in the sludge remarkably decreased when cells were grown under oligotrophic environments. This could be evidence of the cellular energy dissipation caused by ammonia loss and recovery. Intracellular total ammonium nitrogen (TAN) accumulations were observed, which gradually increased from a basal value of ∼1 M (for AOB grown under copious environments) to much higher values (grown under oligotrophic environment). It did not affect the reaction kinetics but potentially served as a reserve against famine.

中文翻译：

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氨氧化细菌（AOB）在不同底物可用性下的底物吸收、损失和储备

摘要 关于亚硝化动力学中真正底物的争论可能是由于细胞的双底物转运系统。我们的实验表明，在富含氨的环境下，它会扩散到膜中（氨是直接底物）；但是，在寡营养条件下，铵离子被主动运输（铵是直接底物）。为了促进这种转变，污泥中的细菌组成发生了变化，尽管在六个恒化器中的大多数中主要是亚硝化单胞菌。此外，底物亲和常数 (Ks) 下降，导致对底物可用性降低的部分补偿。当环境氨浓度低于细胞质浓度时，出现向后扩散，这可能使细胞加速其耗能的铵运输。当细胞在贫营养环境下生长时，氨氧化细菌（AOB）占污泥中细菌总数的百分比显着降低。这可能是由氨损失和恢复引起的细胞能量耗散的证据。观察到细胞内总铵态氮 (TAN) 积累，从基础值 ∼1 M（对于在丰富环境下生长的 AOB）逐渐增加到更高的值（在贫营养环境下生长）。它不会影响反应动力学，但可能用作对抗饥荒的储备。这可能是由氨损失和恢复引起的细胞能量耗散的证据。观察到细胞内总铵态氮 (TAN) 积累，从基础值 ∼1 M（对于在丰富环境下生长的 AOB）逐渐增加到更高的值（在贫营养环境下生长）。它不会影响反应动力学，但可能用作对抗饥荒的储备。这可能是由氨损失和恢复引起的细胞能量耗散的证据。观察到细胞内总铵态氮 (TAN) 积累，从基础值 ∼1 M（对于在丰富环境下生长的 AOB）逐渐增加到更高的值（在贫营养环境下生长）。它不会影响反应动力学，但可能用作对抗饥荒的储备。