Multi-omics provides functional insights and underscores practical challenges in assessing the composition and performance of a nitrifying microbial consortium.

Microbial consortia show promise for bioremediation of environmental pollution, but performance optimization and risk assessment remain challenging due to unculturable species and limitations of traditional biochemical and sequencing tools. This study demonstrates how a multi-omics approach can provide deeper insight into the performance and risks of using a model aerobic ammonia-oxidizing consortium under conditions representative of wastewater treatment. Long-read DNA sequencing recovered several high-quality genomes, revealing dominance by an unclassified IMPORTANCE: Microbial consortia are increasingly used to advance a sustainable bioeconomy. Optimizing consortia for environmental applications and ensuring regulatory compliance remains challenging, largely due to reliance on culturing microbes with unknown physiology. In this study, we apply cutting-edge sequencing to a consortium designed for ammonia removal from wastewater. Long-read DNA sequencing enabled complete genome recovery and revealed that populations integral to nitrogen cycling are poorly represented in taxonomic databases. By integrating multi-omics with biochemical assays, we uncovered how environmental conditions drive off-target nitrogen reactions and the potential risks of exposure to pathogens carrying virulence genes. Our findings underscore how whole-community approaches provide insights that are not obtainable with traditional amplicon sequencing and biochemical analysis methods. However, our study also provides recommendations on how hurdles related to data integration and environmental representation must be addressed to support stakeholders adopting such approaches in the context of commercializing microbial consortia.