Dissimilatory nitrate reduction to ammonium in four Pseudomonas spp. under aerobic conditions

Xuejiao Huang; Luoluo; Deti Xie; Zhenlun Li

doi:10.1016/j.heliyon.2023.e14983

Dissimilatory nitrate reduction to ammonium in four Pseudomonas spp. under aerobic conditions

Heliyon. 2023 Mar 28;9(4):e14983. doi: 10.1016/j.heliyon.2023.e14983. eCollection 2023 Apr.

Authors

Xuejiao Huang^{1

2}, Luoluo¹, Deti Xie², Zhenlun Li²

Affiliations

¹ Key Laboratory of (Guang Xi) Agricultural Environment and Products Safety,College of Agronomy, Guangxi University, Nanning 530004, China.
² Chongqing Key Laboratory of Soil Multiscale Interfacial Process, Southwest University, Chongqing 400716, China.

Abstract

Dissimilatory nitrate reduction to ammonium (DNRA) has an important role in soil nitrogen retention and is considered to be constrained to anaerobic conditions. However, a recent study found that Pseudomonas putida Y-9 is capable of DNRA under aerobic conditions. In this study, four species of Pseudomonas spp. were found to produce ammonium during the nitrite reduction process under aerobic conditions, similar to the Y-9 strain. The detectable ammonium in the culture supernatant during the nitrite reduction process for each of the four strains originated intracellularly. A subsequent ¹⁵N isotope experiment showed that these four strains were able to transform ¹⁵NO₂ ^- to ¹⁵NH₄ ⁺ in 3 h under aerobic conditions. The NirBD sequence in each of the four strains showed high similarity with that in the Y-9 strain (approximately 94.61%). Moreover, the nirBD sequences in the four strains and the Y-9 strain were all similar to those of other Pseudomonas spp., while they were relatively distant in terms of their phylogenetic relationship from those of other genera. Overall, these results suggest that these four strains of Pseudomonas spp. are capable of DNRA under aerobic conditions, which might be attributed to the existence of nirBD.

Keywords: 15N-incubation experiments; Aerobic conditions; Dissimilatory nitrate reduction to ammonium; Pseudomonas spp.; nirBD.