A Novel Nitrogen Metabolism Pathway in Strain Gordonia sp. TD-46: Genomic and Enzymatic Evidence

With the acceleration of industrialization, water pollution caused by ammonia-nitrogen compounds has become a severe environmental challenge. In recent years, significant breakthroughs in biological nitrogen removal technology have been achieved alongside the discovery of novel ammonia-nitrogen-degrading bacterial strains. This study delves into the metabolic pathways and molecular mechanisms of ammonia-nitrogen degradation by Gordonia sp. TD-46. A comprehensive understanding of the strain's nitrogen metabolic pathways and the functions of key genes was achieved by optimizing its ammonia-nitrogen degradation conditions, analyzing its whole-genome sequence, and conducting heterologous expression of crucial genes. The results demonstrated that when ammonium chloride served as the nitrogen source, sodium acetate as the carbon source, with a C/N ratio of 25, pH of 7, and an inoculum size of 15%, the strain achieved an ammonia-nitrogen degradation rate exceeding 80% under these conditions. Whole-genome sequencing analysis identified genes involved in nitrogen metabolism, including glnA, gdhA, narB, narGHI, nirBD, and nasBDE. These genes indicate that the nitrogen metabolism pathway of strain TD 46 follows the assimilatory nitrate reduction pathway (NO₃^- → NO₂^- → NH₄⁺) and the ammonia assimilation pathway (NH₄⁺ → Gln → Glu). Thus, strain TD-46 is capable of efficient nitrogen assimilation.