Isolation and Identification of Respiratory Nitrate Reductase-Producing Bacteria from Soil and Production of the Enzyme

A bacterial strain MY-12, isolated from rice field soil, and identified as Enterobacter cloacae, produced much nitrate reductase in cells in anaerobic culture. Tests were conducted on the growth conditions for anaerobic production of the enzyme. Nitrate was essential for enzyme formation, and iron ions promoted enzyme production. The addition of peptone (2g/liter) to the synthetic medium increased enzyme production with an increase in growth. The specific activity of the enzyme of this strain, cultured under optimal growth conditions, was higher than that of enzyme of Escherichia coli, Klebsiella aerogenes, Bacillus licheniformis or Micrococcus denitrificans. Nitrate reductase of E. cloacae MY-12 produced in anaerobic culture was membrane-bound. Some properties of the solubilized enzyme are described.