A novel HN-AD strain Paenibacillus glycanilyticus DQ-1 with high-efficiency nitrogen removal capacity: genomic insights into its nitrogen metabolic mechanism

The rapid expansion of the aquaculture industry has intensified the discharge of nitrogen-rich wastewater, posing significant ecological risks. Biological treatment with HN-AD bacteria is sustainable, but most conventional strains lack long-term environmental resilience. The key bottleneck is identifying novel, robustly adaptable strains, especially spore-forming Gram-positive bacteria. Moreover, the non-canonical metabolic mechanisms that distinguish such strains remain largely unexplored. This study isolated a novel HN-AD strain, Paenibacillus glycanilyticus DQ-1, from aquaculture sludge and investigated its nitrogen removal performance and genomic metabolic pathways. Strain DQ-1 was isolated and identified through 16 S rRNA gene sequencing and morphological analysis. Its nitrogen removal efficiency was evaluated under aerobic conditions with different nitrogen sources, including ammonium nitrogen (NH₄+-N), nitrate nitrogen (NO₃−-N), total inorganic nitrogen (TIN) and hydroxylamine nitrogen (NH2OH-N). Whole-genome sequencing was conducted using the PacBio Sequel II platform to identify functional genes and reconstruct the nitrogen metabolic pathways. Strain DQ-1 achieved 93.26% NH₄⁺-N and 100% NO₃⁻-N removal within 36 h, with 95.92% TIN removal. Genomic analysis revealed a complete assimilatory nitrate reduction pathway (nasAB and nirBD). Notably, while the canonical hydroxylamine oxidoreductase gene (hao) is absent, the strain showed 74.67% NH2OH-N removal and harbors a putative ammonia monooxygenase gene (amo). These results suggest that DQ-1 employs a novel non-canonical pathway, distinct from known HN-AD models, for efficient nitrogen transformation. P. glycanilyticus DQ-1 differs from typical HN-AD bacteria in its spore-forming ability and a novel hao-independent pathway. This study provides the first comprehensive genomic insight into the nitrogen removal capacity of P. glycanilyticus, expanding the microbial resource pool for sustainable environmental remediation.