• AOA and comammox bacteria can be more abundant and active than AOB/NOB at WWTPs.• Coupled DNRA/anammox and NOx-DAMO/anammox/comammox processes are demonstrated.• Substrate level, SRT and stressors determine the niches of overlooked microbes.• Applications of overlooked microbes in enhancing nitrogen removal are promising. Nitrogen-cycling microorganisms play key roles at the intersection of microbiology and wastewater engineering. In addition to the well-studied ammonia oxidizing bacteria, nitrite oxidizing bacteria, heterotrophic denitrifiers, and anammox bacteria, there are some other N-cycling microorganisms that are less abundant but functionally important in wastewater nitrogen removal. These microbes include, but not limited to ammonia oxidizing archaea (AOA), complete ammonia oxidation (comammox) bacteria, dissimilatory nitrate reduction to ammonia (DNRA) bacteria, and nitrate/nitrite-dependent anaerobic methane oxidizing (NOx-DAMO) microorganisms. In the past decade, the development of high-throughput molecular technologies has enabled the detection, quantification, and characterization of these minor populations. The aim of this review is therefore to synthesize the current knowledge on the distribution, ecological niche, and kinetic properties of these “overlooked” N-cycling microbes at wastewater treatment plants. Their potential applications in novel wastewater nitrogen removal processes are also discussed. A comprehensive understanding of these overlooked N-cycling microbes from microbiology, ecology, and engineering perspectives will facilitate the design and operation of more efficient and sustainable biological nitrogen removal processes. 相似文献
• Comammox bacteria have unique physiological characteristics.• Comammox bacteria are widely distributed in natural and artificial systems.• Comammox bacteria have the potential to reduce N2O emissions.• Coupling comammox bacteria with DEAMOX can be promoted in wastewater treatment.• Comammox bacteria have significant potential for enhancing total nitrogen removal. Complete ammonia oxidizing bacteria, or comammox bacteria (CAOB), can oxidize ammonium to nitrate on its own. Its discovery revolutionized our understanding of biological nitrification, and its distribution in both natural and artificial systems has enabled a reevaluation of the relative contribution of microorganisms to the nitrogen cycle. Its wide distribution, adaptation to oligotrophic medium, and diverse metabolic pathways, means extensive research on CAOB and its application in water treatment can be promoted. Furthermore, the energy-saving characteristics of high oxygen affinity and low sludge production may also become frontier directions for wastewater treatment. This paper provides an overview of the discovery and environmental distribution of CAOB, as well as the physiological characteristics of the microorganisms, such as nutrient medium, environmental factors, enzymes, and metabolism, focusing on future research and the application of CAOB in wastewater treatment. Further research should be carried out on the physiological characteristics of CAOB, to analyze its ecological niche and impact factors, and explore its application potential in wastewater treatment nitrogen cycle improvement. 相似文献