Trash to treasure: exploring the wastewater system with high quality MAGs from large-scale Nanopore data

Improvements to wastewater resource recovery and treatment efficiency are essential for fulfilling the UN sustainable development goals for both sustainable cities (goal 11) and responsible production and consumption (goal 12). Microbes are central to the processes underpinning wastewater treatment, however knowledge of this complex community is limited to isolates, marker genes or incomplete genomes. To improve our capacity to characterise this community at the genome level, we conducted large-scale long-read sequencing of 23 Danish full-scale wastewater treatment plant (WWTP) metagenomes using the Nanopore PromethION platform, producing >1 Tbp (or 17 TB raw) of long-read data. These data enabled the recovery of 987 metagenome-assembled genomes (MAGs), including 36 circular genomes, after short-read data polishing (>0.9 Tbp Illumina). The recovered MAGs met stringent high-quality draft requirements of >90% completeness, <5% contamination and full-length rRNA genes. The MAGs included known and uncharacterised, abundant and rare lineages, and accounted for 25% of the populations present in the metagenomes. With these MAGs we present a HQ reference database for WWTP systems that will facilitate the connection of genomic potential to historical and future amplicon studies.