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

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 Y-9 is capable of DNRA under aerobic conditions. In this study, four species of 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 N isotope experiment showed that these four strains were able to transform NO to NH 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 sequences in the four strains and the Y-9 strain were all similar to those of other 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 spp. are capable of DNRA under aerobic conditions, which might be attributed to the existence of .