Seasonal Prevalence of Ammonia-Oxidizing Archaea in a Full-Scale Municipal Wastewater Treatment Plant Treating Saline Wastewater Revealed by a 6‑Year Time-Series Analysis

Although several molecular-based
studies have demonstrated the
involvement of ammonia-oxidizing archaea (AOA) in ammonia oxidation
in wastewater treatment plants (WWTPs), factors affecting the persistence
and growth of AOA in these engineered systems have not been resolved.
Here, we show a seasonal prevalence of AOA in a full-scale WWTP (Shatin,
Hong Kong SAR) over a 6-year period of observation, even outnumbering
ammonia-oxidizing bacteria in the seasonal peaks in 3 years, which
may be due to the high bioavailable copper concentrations. Comparative
analysis of three metagenome-assembled genomes of group I.1a AOA obtained
from the activated sludge and 16S rRNA gene sequences recovered from
marine sediments suggested that the seawater used for toilet flushing
was the primary source of the WWTP AOA. A rare AOA population in the
estuarine source water became transiently abundant in the WWTP with
a metagenome-based relative abundance of up to 1.3% over three seasons
of observation. Correlation-based network analysis revealed a robust
co-occurrence relationship between these AOA and organisms potentially
active in nitrite oxidation. Moreover, a strong correlation between
the dominant AOA and an abundant proteobacterial organism suggested
that capacity for extracellular polymeric substance production by
the proteobacterium could provide a niche for AOA within bioaggregates.
Together, the study highlights the importance of long-term observation
in identifying biotic and abiotic factors governing population dynamics
in open systems such as full-scale WWTPs.

尽管多项基于分子生物学的研究已证实氨氧化古菌（ammonia-oxidizing archaea, AOA）参与污水处理厂（wastewater treatment plants, WWTPs）的氨氧化过程，但这类工程系统中影响AOA存续与生长的调控因子仍未明确。本研究对香港特别行政区（Hong Kong SAR）沙田区一座全规模污水处理厂展开了为期6年的跟踪观测，结果显示AOA在该设施中呈现显著的季节分布规律：在其中3个年份的季节峰值时段，其丰度甚至超过了氨氧化细菌，这一现象或与水体中较高的生物可利用铜浓度密切相关。研究人员从该污水处理厂的活性污泥中获取了3株I.1a类群AOA的宏基因组组装基因组（metagenome-assembled genomes），并结合从海洋沉积物中获得的16S rRNA基因序列开展比较分析，结果表明用于冲厕的海水是该污水处理厂中AOA的主要来源。源自河口源水的稀有AOA类群在该设施中出现暂时性富集，在三轮观测季节中，基于宏基因组分析的相对丰度最高可达1.3%。基于相关性的网络分析显示，这类AOA与潜在具备亚硝酸盐氧化活性的微生物之间存在稳固的共现关联。此外，优势AOA类群与一种高丰度变形菌门微生物之间存在强相关性，提示该变形菌通过合成胞外聚合物（extracellular polymeric substance, EPS）的能力，可为生物聚集体中的AOA提供生存微环境。综上，本研究凸显了长期观测的重要意义，其有助于明确全规模污水处理厂这类开放系统中调控微生物种群动态的生物与非生物因子。