Metagenomic evidence of new anammox bacteria in a groundwater with extreme nitrate and ammonium pollution nearby uranium sludge repository

The process of anaerobic ammonium oxidation (anammox) is an essential part of global nitrogen cycle. To date, anammox bacteria belong to six Candidatus genera and have been discovered in various anthropogenic and natural habitats, including weakly and heavily nitrogen-polluted aquifers. In this work, using fluorescent in situ hybridization and 16S rRNA gene sequencing, anammox bacteria were detected for the first time in the groundwater ecosystem with extreme anthropogenic nitrogen pollution and low year-round temperature in the zone of a radioactive waste surface repository. Further metagenomic analysis resulted in retrieval of four distinct anammox metagenome-assembled genomes (MAGs), representing a new genus of Brocadiaceae familie , new species in Ca. Kuenenia, and two strains of a new species in Ca. Scalindua. The high abundance of the new anammox community in this unique polluted aquifer suggests their potential use for sustainable bioremediation in the near future.