Isolation and culture conditions of a klebsiella pneumoniae strain that can utilize ammonium and nitrate ions simultaneously with controlled iron and molybdate ion concentrations

A bacterial strain F-5-2, isolated from soil and identified as Klebsiella pneumoniae, removed NH₄⁺ completely in 24 h of aerobic cultivation in a medium containing 1 mg/ml of NH₄NO₃. However, 70% of the NO₃⁻ originally provided remained. When 100 μM Fe²⁺ was added to the medium, both NH₄⁺ and NO₃⁻ were removed simultaneously and completely from the culture within 6 h of incubation. In addition, the amount of MoO₄⁻ in the medium markedly affected the bacterial cell growth and utilization of NH₄⁺ and NO₃⁻. The bacterium could remove 4 mg/ml of NH₄NO₃ completely in 48 h of aerobic cultivation in a medium containing 100 μM Fe²⁺ and 0.8 pM MoO₄²⁻. The total nitrogen in the culture containing its cells was decreased to 14% of that in the NH₄NO₃ originally provided. GC-MS analysis demonstrated that N₂ was generated from the nitrogen atoms of both NH₄⁺ and NO₃⁻.