Biologically catalysed reduction of nitrous oxide (N₂O, laughing gas) to dinitrogen gas is a desirable process in view of the increasing atmospheric concentration of this important greenhouse gas and ozone-depleting substance [1]. A diverse range of bacterial species produce the copper cluster-containing enzyme N₂O reductase (NosZ). Based on phylogenetic analyses, NosZ enzymes have been classified as clade I or clade II, and the corresponding organisms are expected to differ significantly in their electron transport processes to NosZ as well as in the maintenance and repair of the NosZ active site. In some organisms, N₂O reduction contributes to a distinct mode of anaerobic respiration, termed N₂O respiration [2].

In the present study, the N₂O-respiring and nitrate-ammonifying soil organism Neobacillus vireti (phylum Bacillota) [3] was investigated for its ability to reduce N₂O in pure cultures and in soil microcosms when introduced as vegetative cells or spores. The abundance of added N. vireti cells in soil microcosms was determined by qPCR using appropriate primer pairs.

Specific N₂O turnover rates, apparent N₂O affinities and survival of N. vireti cells in soil will be presented.

The data suggest that N. vireti cells are a potential candidate for use in mitigating nitrous oxide emissions from agricultural soils, the largest anthropogenic source of N2O [1].

References

1 Tian H, Xu R, Canadell JG, Thompson, RL, Winiwarter W et al. (2020) A comprehensive quantification of global nitrous oxide sources and sinks. Nature 586, 248–256

2 Hein S & Simon J (2019) Bacterial nitrous oxide respiration: electron transport chains and copper transfer reactions. Adv. Microb. Physiol. 75, 137–175

3 Mania D, Heylen K, van Spanning RJM & Frostegård Å (2014) The nitrate-ammonifying and nosZ-carrying bacterium Bacillus vireti is a potent source and sink for nitric and nitrous oxide under high nitrate conditions. Environ. Microbiol. 16, 3196–3210