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<p>The identification of complete ammonia oxidizers (comammox) within the nitriteoxidizing bacteria (NOB) genus <i>Nitrospira</i>, capable of oxidizing ammonia directly to nitrite and nitrate, represents a pivotal advancement in elucidating the microbial and metabolic pathways underlying nitrification in the global nitrogen cycle. Although comammox <i>Nitrospira</i> have been consistently identified across diverse environmental habitats, their rapid enrichment from complex activated sludge systems remains challenging owing to their intrinsically low growth rates and the restricted availability of cultured isolates. In this study, <i>Candidatus Nitrospira inopinata</i> (<i>Ca. N. inopinata</i>) was successfully enriched from anammox-inoculated sludge within 70 d under low ammonia concentrations (~4.88 mg/L), ambient temperatures (21.6–28.4 °C), and minimal aeration (0–0.01 mg/L), facilitated by the application of kanamycin (KAN). By employing 16S rRNA gene amplicon sequencing and quantitative polymerase chain reaction (qPCR) targeting the functional marker gene <i>amoA, Ca. N. inopinata</i> was identified as the dominant ammonia oxidizer, achieving a relative abundance of 95.22% in the nitrifying community. Kanamycin was shown to exert significant selective pressure, further enhancing the enrichment of <i>Ca. N. inopinata</i>. These findings demonstrate the feasibility of establishing comammox <i>Nitrospira</i> through direct inoculation of anammox pellets coupled with kanamycin, offering a robust and efficient strategy for rapid enrichment of comammox <i>Nitrospira</i> for biotechnological applications, while underscoring the energy-efficient advantages of comammox-driven ammonia oxidation processes.</p>

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Rapid enrichment of Ca. Nitrospira inopinata using anammox and kanamycin: a path toward sustainable nitrification

  • 期刊论文

  • 发表日期：

    2025年5月26日

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  • Hongwei Sun,
  • Xiaoli Li,
  • Xintao Lv,
  • Zhiming Qu,
  • Xiaoyong Yang,
  • Gang Wang,
  • Yanxiang Zhang,
  • Yucan Liu,
  • Shujun Zhang

摘要

The identification of complete ammonia oxidizers (comammox) within the nitriteoxidizing bacteria (NOB) genus Nitrospira, capable of oxidizing ammonia directly to nitrite and nitrate, represents a pivotal advancement in elucidating the microbial and metabolic pathways underlying nitrification in the global nitrogen cycle. Although comammox Nitrospira have been consistently identified across diverse environmental habitats, their rapid enrichment from complex activated sludge systems remains challenging owing to their intrinsically low growth rates and the restricted availability of cultured isolates. In this study, Candidatus Nitrospira inopinata (Ca. N. inopinata) was successfully enriched from anammox-inoculated sludge within 70 d under low ammonia concentrations (~4.88 mg/L), ambient temperatures (21.6–28.4 °C), and minimal aeration (0–0.01 mg/L), facilitated by the application of kanamycin (KAN). By employing 16S rRNA gene amplicon sequencing and quantitative polymerase chain reaction (qPCR) targeting the functional marker gene amoA, Ca. N. inopinata was identified as the dominant ammonia oxidizer, achieving a relative abundance of 95.22% in the nitrifying community. Kanamycin was shown to exert significant selective pressure, further enhancing the enrichment of Ca. N. inopinata. These findings demonstrate the feasibility of establishing comammox Nitrospira through direct inoculation of anammox pellets coupled with kanamycin, offering a robust and efficient strategy for rapid enrichment of comammox Nitrospira for biotechnological applications, while underscoring the energy-efficient advantages of comammox-driven ammonia oxidation processes.