Temperature modulates stress response in anammox reactors

Anaerobic ammonium oxidation (anammox) is a promising energy-efficient mechanism of nitrogen removal in wastewater treatment plants (WWTPs). However, deployment for mainstream WWTPs remains challenging as the response dynamics of anammox biofilms to stresses such as fluctuations in dissolved oxygen and temperature are poorly understood. Here, we investigated the response of microbial biofilm communities with verified anammox activity to transient oxygen perturbations under different temperature regimes. A novel approach using genome-centric metagenomics paired with metatranscriptomics allowed us to investigate the transcriptional stress response from individual key members of the community. The temperature regime and strength of oxygen perturbations induced divergent responses from the process level down to the transcription profile of individual taxa. We show that the temperature results in distinct transcriptional states of compositionally identical communities and even of phylogenetically related bacterial species. Our findings improve the current understanding of how process disruptions affect microbial communities on various ecosystem and biological levels.