The nitrate-ammonifying and nosZ-carrying bacterium Bacillus vireti is a potent source and sink for nitric and nitrous oxide under high nitrate conditions.
Several Gram-positive bacteria carry genes for anaerobic reduction of NO3(-) via NO2(-) to NH4(+) or gaseous nitrogen compounds, but the processes are understudied for these organisms. Here, we present results from a whole-genome analysis of the soil bacterium Bacillus vireti and a phenotypic characterization of intermediate and end-products, formed under anoxic conditions in the presence of NO3(-). Bacillus vireti has a versatile metabolism. It produces acetate, formate, succinate and lactate from fermentation and performs dissimilatory nitrate reduction via NO2(-) to ammonium (DNRA) using NrfA, while NirB may detoxify NO2(-) in the cytoplasm. Moreover, it produces NO from an unknown source and reduces it via N2O to N2 using two enzymes connected to denitrification: an unusual NO reductase, qCuA Nor encoded by cbaA, and a z-type N2O reductase, encoded by nosZ. In batch cultures, B. vireti reduced all NO3(-) to NO2(-) before the NO2(-) was reduced further. The quantities of all products varied with the initial NO3(-) concentration. With 5 mM NO3(-) , 90% was reduced to NH4 (+) while with ≥ 20 mM NO3(-), 50% was reduced to NO, N2O and N2. This organism is thus an aggressive NO2(-) accumulator and may act as a net source and sink of NO and N2O.
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Science, Ås, Norway.
Daniel
D
Mania
Kim
K
Heylen
Rob J M
RJ
van Spanning
Asa
A
Frostegård
D064751:Ammonium Compounds / Q000378:metabolism; D001407:Bacillus / Q000235:genetics / Q000378:metabolism*; D058440:Denitrification; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics
D064751:Ammonium Compounds; D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; D010088:Oxidoreductases; D009609:Nitrous Oxide; D009584:Nitrogen