Temperature modulates stress response in anammox reactors

Autotrophic nitrogen removal by anaerobic ammonium oxidizing (anammox) bacteria is an energy-efficient nitrogen removal process in wastewater treatment. However, full-scale deployment under mainstream conditions remains challenging for practitioners due to the high stress susceptibility of anammox bacteria towards fluctuations in dissolved oxygen and temperature. Here, we investigated the response of microbial biofilms with verified anammox activity to oxygen shocks under favorable and cold temperature regimes. Genome-centric metagenomics and metatranscriptomics were used to investigate the stress response on various biological levels. We show that temperature regime and strength of oxygen perturbations induced divergent responses from the process level down to the transcriptional profile of individual taxa. Temperature induced distinct transcriptional states in compositionally identical communities and transient pulses of dissolved oxygen resulted in the upregulation of stress-response only under favorable temperatures. Anammox species and other key biofilm taxa display different transcriptional responses to the induced stress regimes.