Degradation Pathway and Nitrogen Metabolism Mechanism of a Heterotrophic Nitrifying Bacterium with High Efficiency in Pyridine Degradation

In this study, a strain with high efficiency in pyridine degradation, Rhodococcus pyridinivorans WN2, was isolated and identified, and systematic research was conducted on the biological characteristics and mechanisms of its pyridine degradation. The environmental conditions (pH, temperature, dissolved oxygen, and salinity) for pyridine degradation were optimized based on single-factor experiments. The pyridine degradation rate, mineralization rate, and maximum tolerance concentration of pyridine were investigated under different pyridine concentrations. The pyridine degradation pathway was explored based on the identification of intermediate products of pyridine degradation. Combined with15N isotope tracing technology, nitrogen balance analysis was carried out on the transformation process of ammonia nitrogen produced after pyridine ring opening, and the distribution ratio of assimilatory (cell synthesis) and dissimilatory (gaseous products) nitrogen was quantified. Furthermore, transcriptome sequencing analysis under pyridine stimulation was performed to identify differentially expressed functional genes and reveal the carbon and nitrogen transformation pathways during pyridine metabolism. This study provides a theoretical basis for the application of pyridine-degrading bacteria in the treatment of high-concentration pyridine-containing organic wastewater.