Predominance of comammox bacteria among ammonia oxidizers under low dissolved oxygen condition

• Published in: Chemosphere (Oxford) 2022-12, Vol.308, p.136436-136436, Article 136436
• Main Authors: Zheng, Maosheng, Mu, Guangli, Zhang, Anqi, Wang, Jiawen, Chang, Fang, Niu, Junfeng, Wang, Xinwei, Gao, Tian, Zhao, Zhirong
• Format: Article
• Language: English
• Subjects: Ammonia oxidizing microorganisms; Comammox; Low oxygen; Niche differentiation
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2022.136436

Although low-oxygen nitrification can significantly cut down the aeration demand in wastewater treatment plants, little is known about the community dynamics of relevant microorganisms under different oxygen concentrations. Here, by conducting a series of bioreactors with oxygen concentrations of 0%, 2%, 5%, 10%, 20%, 40%, and 70%, we provided a comprehensive investigation on the behaviors and performances of comammox bacteria (CMX), ammonia-oxidizing bacteria (AOB) and archaea (AOA) during the nitrification process. Quantitative PCR analysis demonstrated that CMX was the dominant ammonia-oxidizer under low oxygen condition (10%) after the four-month operation with the abundance increased by 8.65 times higher than the initial operation, whereas the growth of AOA and AOB was inhibited. Moreover, Nitrospira nitrosa dominated the CMX species (relative abundance >96%) in low dissolved oxygen concentrations, while Nitrospira nitrificans (3.39%) seemed to prefer high oxygen conditions. Our study indicates the long-term effects of oxygen concentrations on the niche differentiation of ammonia oxidizers, and highlights the significance of CMX in low-oxygen nitrification for reducing global carbon emission and energy consumption. [Display omitted] •AOB, AOA, and CMX exhibited niche differentiation under different oxygen contents.•CMX was enriched while AOB and AOA were inhibited in low oxygen nitrification.•Nitrospira nitrosa was the most abundant CMX species under low oxygen conditions.•Regulating CMX contributes to energy-saving and consumption-reduction in WWTPs.