Community succession of anammox biofilms in engineered ecosystems

Complex microbial biofilms orchestrating mainstream anaerobic ammonium oxida-tion (anammox) represent one of the most promising energy-efficient mechanisms of fixed nitrogen elimination from anthropogenic waste waters. However, little is known about the ecological processes that are driving microbial community assem-bly leading to functional anammox biofilms in engineered ecosystems. Here, we use fluorescence in situ hybridization and 16S rRNA sequencing combined with network modelling to elucidate the contribution of stochastic and deterministic processes dur-ing anammox biofilm development from first colonization to maturation. We find that distinct development stages emerge naturally in terms of structure and commu-nity composition during biofilm formation. These distinct stages are characterized by a dynamic interplay of stochastic and deterministic processes and appear to be a pre-requisite for the growth of anammox bacteria and to reach biofilm community struc-ture with the desired metabolic capacities. We discuss the relevance of this improved understanding of anammox community ecology and development with regards to its practical application in the start-up and configuration of anammox biofilm reactors.