Discovery of a new genus of anaerobic ammonium oxidizing bacteria with a mechanism for oxygen tolerance

•A new genus of anammox bacteria retrieved from the biofilm system of a full-scale WWTP.•The new genus is named Candidatus Loosdrechtia aerotolerans.•It has gene for the dissimilatory nitrate reduction to ammonium pathway in addition to the core anammox reactions.•A new ferredoxin-dependent nitrate reductase is detected in this genus.•Its oxygen tolerance is likely due to bilirubin oxidase, cytochrome c oxidase and the bifunctional catalase-peroxidase.