A novel Schinkia sp. respires nitrous oxide over a broad pH range

Known bacteria reduce the climate-active gas nitrous oxide (N 2 O) to dinitrogen (N 2 ) over narrow pH ranges, limiting their efficacy in pH heterogeneous soil environments. A dual pH (pH 4.5 → 7.0 → 4.5) enrichment strategy with N 2 O as electron acceptor yielded a novel Schinkia isolate, strain CFF1, capable of N 2 O reduction over broad pH (4.5–8.5) and salinity (1–20 g L −1 NaCl) ranges. Strain CFF1 couples complete fumarate oxidation with N 2 O respiration and produces 10.2 ± 2.4 mg of biomass (dry weight) per mmol N 2 O consumed. Fumarate, succinate, lactate, pyruvate, and propionate, but not acetate, formate, or hydrogen, support N 2 O respiration. N 2 O reduction rates of 6.13 ± 0.30 µmol N 2 O (mg biomass hour) −1 were measured at pH 7.5, with ~30% lower rates observed at pH 4.5 and 8.5. Acetylene (33%, vol/vol), a potent inhibitor of N 2 O reductase (NosZ), had no impact on the growth of strain CFF1 with N 2 O. Alternate growth-supporting electron acceptors include nitrate, nitrite, and O 2 . Genomic investigations revealed four distinct clade II nosZ genes, and proteomic measurements demonstrated the synthesis of the same two NosZ under both acidic and alkaline growth conditions. Physiological characterization and phylogenomic analysis indicate the isolate represents a new species in the genus Schinkia , for which the name Schinkia acidoalkalinis strain CFF1 is proposed. A soil isolate capable of reducing N 2 O over a broad pH range expands our understanding of the ecophysiology of N 2 O-reducing bacteria and N 2 O turnover in environments where pH varies across space and time. IMPORTANCE Dissimilatory N 2 O reduction catalyzed by the N 2 O reductase NosZ is the major process consuming the climate-active gas N 2 O. Known N 2 O-reducing microorganisms operate within narrow pH windows, potentially limiting N 2 O turnover in heterogeneous soil environments. We isolated Schinkia acidoalkalinis strain CFF1 capable of reducing N 2 O at similar rates over a broad pH range spanning pH 4.5–8.5. The discovery of an N 2 O-reducing pH generalist expands opportunities for developing robust biotechnologies to enhance N 2 O consumption in natural and engineered systems characterized by pH heterogeneity.