Nitrous oxide reductase (nosZ) from wastewater
This study explores the genetic landscape of nitrous oxide (N2O) reduction in wastewater treatment plants (WWTPs) by profiling 1083 high-quality metagenome-assembled genomes (HQ MAGs) derived from 23 Danish full-scale WWTPs. The analysis focuses on the distribution and diversity of nitrous oxide reductase (nosZ) genes, key players in N2O reduction, and their connection to other nitrogen metabolism pathways. A custom pipeline for clade-specific nosZ gene identification outperformed existing methods, revealing the presence of 503 nosZ sequences in 489 MAGs. Notably, 48.7% of the MAGs harboured nosZ genes, with clade II dominating (92.3%). Taxonomic profiling reveals the distribution of nosZ clade I and clade II-containing MAGs, emphasizing the dominance of Bacteroidota and Pseudomonadota. Notably, Chloroflexota exhibits unexpected affiliations with nosZ clade I. The taxonomic diversity of non-denitrifying N2O-reducers is also explored, highlighting the presence of these organisms in Bacteroidota, Chloroflexota, and other phyla.