Efficient nitrogen removal via simultaneous ammonium assimilation and heterotrophic denitrification of R-1.

Although diverse microorganisms can remove ammonium and nitrate simultaneously, their metabolic mechanisms are not well understood. R-1 showed the maximal NH removal rate 9.94 mg L·h and 2.91 mg L·h under aerobic and anaerobic conditions, respectively. Analysis of the nitrogen balance calculation and isotope tracing experiment indicated that NH was consumed through assimilation. The maximal NO removal rate of strain R-1 was 18.05 and 19.76 mg L·h under aerobic and anaerobic conditions, respectively. The stoichiometric consumption ratio of acetate to nitrate was 0.902 and NO was reduced to N for strain R-1 through NO isotopic tracing experiment, which indicated a respiratory process coupled with the oxidation of electron donors. Genomic analysis showed that strain R-1 contained genes for ammonium assimilation and denitrification, which effectively promoted each other. These findings provide insights into microbial nitrogen transformation and facilitate the simultaneous removal of NH and NO in a single reactor.