Unlocking NO respiratory pathways in Stutzerimonas stutzeri PRE-2: Implications for reducing NO emissions from estuaries.

Although nitrogen cycling in nitrogen-enriched estuaries is highly active, the reported nitrous oxide (NO) emission factor (EF) values for NO emissions in estuarine environments are usually low. Therefore, biological or abiotic mechanisms control the emission of NO from estuarine ecosystems. In this study, a pure culture of NO-reducing bacteria was isolated from Pearl River Estuary surface sediment and identified as Stutzerimonas stutzeri PRE-2. This strain displayed a high NO reduction capability, and the average NO reduction rate was 17.93 ± 0.43 μmol h under anoxic conditions. This reduction of NO was coupled with the stoichiometric consumption of acetate or lactate as electron donors, suggesting that microbial NO reduction involves electron transport. Furthermore, NO reduction can yield energy that supports microbial growth. Genomic analysis demonstrated that the strain Stutzerimonas stutzeri PRE-2 contains a complete pathway for the reduction of NO to N. Typical respiratory chain inhibitors did not significantly inhibit NO reduction activity, demonstrating that the electron transfer pathway involved in NO reduction is unique compared to the classic respiratory chain. The integrated evidence suggests that microbial NO reduction by Stutzerimonas stutzeri PRE-2 involves NO respiration and may play an important role in reducing NO emissions in estuarine ecosystems.