The Relationship between Ribosomal RNA Operon Copy Number and Ecological Characteristics of Activated Sludge Microbial Communities across China

It is well accepted that the high performance of wastewater treatment plants (WWTPs) relies on the microbial community in activated sludge (AS). Hence, it is crucial to illuminate the geographic distributions and influencing factors of the ecological strategies employed by the AS microbial community. Here, we investigated how the ecological strategies of AS microbial communities influenced their ecological characteristics in 60 WWTPs across 15 cities in China. Our study showed that the average rrn copy number of the whole AS microbial community across China was 2.25 ± 0.12. The highest average rrn copy number of the core community indicated that core members tend to be r-strategists with an advantage in rapid pollutant removal and recovery of the community after environmental disturbances. High nutrient availability promoted microorganisms with higher average rrn copy numbers, while long sludge retention time (SRT) was preferred to the microorganisms with lower average rrn copy numbers. Homogenous selection and dispersal limitation were the predominant assembling processes at the city level, with a shift from deterministic to stochastic processes with increasing average rrn copy numbers. Furthermore, more r-strategists participated in chemoheterotrophic functions, while more K-strategists were related to the nitrification processes. Overall, our findings enrich the knowledge of AS microbial ecology and lay the theoretical foundation for the precise regulation of WWTPs.