FIG 1.

NO₃⁻/NO₂⁻ reduction in batch cultures of S. loihica strain PV-4. All vessels received 10% acetylene (C₂H₂) gas in the headspace for blocking N₂O reduction to N₂. Cultures were amended with 5.0 mM lactate as the electron donor and 1.0 mM NO₃⁻ (A) or 1.0 mM NO₂⁻ (B) as the electron acceptor. The change in the amounts of NO₃⁻ (■), NO₂⁻ (●), NH₄⁺ (□), and N₂O-N (○) in the vessels was monitored until all NO₃⁻ and NO₂⁻ in the medium was reduced to NH₄⁺ and N₂O. The error bars represent the standard deviations from triplicate cultures.