The nitrite reductase encoded by nirBDs in Pseudomonas putida Y-9 influences ammonium transformation
Xuejiao Huang, Yuwen Luo, Luo Luo, Deti Xie, Zhenlun Li
Abstract
It is unknown whether nirBDs , which conventionally encode an NADH nitrite reductase, play other novel roles in nitrogen cycling. In this study, we explored the role of nirBDs in the nitrogen cycling of Pseudomonas putida Y-9. nirBDs had no effect on organic nitrogen transformation by strain Y-9. The △ nirBD strain exhibited higher ammonium removal efficiency (90.7%) than the wild-type strain (76.1%; P < 0.05) and lower end gaseous nitrogen (N 2 O) production. Moreover, the expression of glnA (control of the ammonium assimilation) in the △ nirBD strain was higher than that in the wild-type strain ( P < 0.05) after being cultured in ammonium-containing medium. Furthermore, nitrite noticeably inhibited the ammonium elimination of the wild-type strain, with a corresponding removal rate decreasing to 44.8%. However, no similar impact on ammonium transformation was observed for the △ nirBD strain, with removal efficiency reaching 97.5%. In conclusion, nirBDs in strain Y-9 decreased the ammonium assimilation and increased the ammonium oxidation to nitrous oxide.