The finding of anammox bacteria brought up the possibility of achieving energy-self-sufficient wastewater treatment plants for nitrogen removal, but their widespread technological application is still under research. The lack of pure cultures, standard cultivation methods and comprehensive genetic data make the molecular research on anammox bacteria challenging, and thus, there is a critical absence of molecular studies to understand how these bacteria make a living. One of the current challenges of anammox bacteria research is to understand niche differentiation, meaning how and why different anammox species find their unique ecological space. RESPIMMOX project aims to understand the biomolecular characteristics of anammox Ca. Brocadia that trigger their niche differentiation as the main anammox genus present in wastewater treatment plants, to improve the efficiency and stability of bioreactors. We will obtain biochemical evidence of the membrane-bound protein complexes involved in the electron transport chain of Brocadia-species, and investigate the soluble yet-unidentified enzymes responsible of the nitrite reduction. We will follow a complexome profiling approach combined with enzymatic activity assays, as commonly performed with Dehalococcoides mccartyi in the host laboratory. RESPIMMOX project will be accomplished through three specific objectives: i) achievement of an anammox Brocadia-enriched culture with high cell concentrations; ii) training of the researcher in biochemical methods to characterize respiratory complexes using the respiration with halogenated aromatic compounds as an example; and iii) identification and characterization of the protein complexes involved in the anammox Ca. Brocadia energy metabolism. The results from this proposal will entail a step forward for the understanding of anammox niche differentiation, specifically of the dominance of Ca. Brocadia in bioreactors, and will contribute to unravel the puzzle that anammox bacteria pose.