Metabolic acclimation of anammox consortia to decreased temperature.

Widespread application of anammox process has been primarily limited to the high sensitivity of anammox consortia to fluctuations of temperature. However, the metabolic acclimation of anammox consortia to decreased temperature remains unclear, which is the core of developing potential strategies for improving their low-temperature resistance. Here, we operated anammox reactors at 25 °C and 35 °C to explore the acclimation mechanism of anammox consortia in terms of metabolic responses and cross-feedings. Accordingly, we found that the adaptation of anammox consortia to ambient temperature (25 °C) was significantly linked to energy conservation strategy, resulting in decreased extracellular polymeric substance secretion, accumulation of ATP and amino acids. The expression patterns of cold shock proteins and core enzymes caused the apparent metabolic advantage of Candidatus Brocadia fulgida for acclimation to ambient temperature compared to other anammox species. Importantly, strengthened cross-feedings of amino acids, nitrite and glycine betaine benefited adaptation of anammox consortia to ambient temperature. Our work not only uncovers the temperature-adaptive mechanisms of anammox consortia, but also emphasizes the important role of metabolic cross-feeding in the temperature adaptation of microbial community.