Critical Factors Facilitating Candidatus Nitrotoga To Be Prevalent Nitrite-Oxidizing Bacteria in Activated Sludge

Abstract

Nitrite oxidation is the primary pathway that generates nitrate in engineered systems. However, little is known about the role of a novel nitrite-oxidizing bacteria (NOB) genus Candidatus Nitrotoga in activated sludge systems. To elucidate key factors that impact NOB community composition, laboratory-scale sequencing batch reactors (SBRs) were designed and operated under the same conditions as real wastewater treatment plants to achieve considerable nitrogen removal and similar community; then, different conditions including temperature (T), dissolved oxygen (DO), free nitrous acid (FNA), and free ammonia (FA) were applied. The 16S rRNA gene-based PCR and sequence analysis illustrated that Ca. Nitrotoga were abundant even at ambient temperature, thus further challenging the previous conception of them being solely cold-adapted. Ca. Nitrotoga are less competitive than Nitrospira during oxygen deficiency, indicating its lower affinity to dissolved oxygen. Ca. Nitrotoga are the dominant nitrite oxidizers under regular exposure to FNA and FA due to their relatively higher resistance than other NOB toward these two effective biocides. Therefore, this study demonstrates that Ca. Nitrotoga can play an important role in biological nitrogen removal and also highlights the need for multiple strategies for NOB suppression for the next-generation, shortcut nitrogen removal.

Some like it cold: the cellular organization and physiological limits of cold‐tolerant nitrite‐oxidizing Nitrotoga

“…This might hint at a lifestyle adapted to low oxygen concentrations, which is in accordance with employing a high‐affinity cbb 3 oxidase. Similar to their nitrite affinities, however, the oxygen affinities of Nitrotoga also seem lower than those of Nitrospira (Nowka et al ., 2015a; Zheng et al ., 2020).…”

The structure of microbial communities of activated sludge of large-scale wastewater treatment plants in the city of Moscow

“…This recently described Ca . Nitrotoga species can be functionally and sometimes dominant important nitrite oxidizers in WWTPs due to their relatively higher resistance to free nitrous acid and free ammonia than other NOB and the presence of complete pathways for hydrogen and sulfite oxidation, suggesting that alternative energy metabolisms enable these bacteria to survive nitrite depletion 40 – 42 .…”

Relevance of Candidatus Nitrotoga for nitrite oxidation in technical nitrogen removal systems

“…For instance, close relatives of mesophilic Cand . Nitrotoga fabula were less competitive with Nitrospira at cold conditions and seem to be responsible for nitrite oxidation in warm water (> 20 °C) N-removal systems as observed in China and Australia (Liu et al 2021 ; Zheng et al 2020 ; Petrovski et al 2020 ; Table S1 ).…”

“…However, in an SBR, Cand. Nitrotoga was found to have a lower affinity to dissolved oxygen than Nitrospira (Zheng et al 2020 ; Table 1 and S1 ), and a stepwise increase of the DO level in a PNA reactor from 0.4 to 1.8 mg L −1 (13–56 µM) led to an increase of Cand. Nitrotoga versus Nitrospira (Qian et al 2021 ), which confirmed the tolerance of Cand.…”

“…In accordance, Cand. Nitrotoga became the dominant nitrite oxidizer, while Nitrospira was inhibited in water treatment under exposure to FNA and FA (Li et al 2020 ; Zheng et al 2020 ; Wang et al 2021 ; Table 1 and S1). Similar to Nitrobacter , which revealed a residual activity of 10% in the presence of 1.0 mg HNO 2 -N L −1 (71 µM) (Blackburne et al 2007 ), Cand.…”