Keystone taxa mediate the trade-off between microbial community stability and performance in activated sludges

Abstract

Microbial communities form complex interaction networks where species cooperation is crucial for maintaining stability and performance. However, the key species and their specific roles in maintaining these properties remain poorly understood. Here, to address this, we conducted a large-scale network analysis of microbial communities in 1,186 activated sludge samples worldwide. The resulting activated sludge co-occurrence network exhibited a typical scale-free structure, with most taxa having few connections and a select few being highly interconnected. A group of keystone taxa, distinguished by high connectivity and a critical role in network stability, was identified. Microbial communities harbouring keystone taxa were more stable but exhibited lower pollutant removal rates. Comparative analysis showed that, in response to industrial wastewater inflow, communities with keystone taxa maintained more stable composition and species abundance while achieving similar pollutant removal rates. These results demonstrate that, while keystone taxa are critical for microbial community stability, this stability comes at the cost of reduced function in activated sludge systems. This study provides deeper insights into the link between community composition, stability and function, highlighting the potential to optimize microbial performance by manipulating keystone taxa. A large-scale network analysis of the microbial communities residing in nearly 1,186 activated sludge samples demonstrates an interplay between network stability and pollutant degradation, leveraged mainly by a group of keystone taxa.