OXYGEN-DEPENDENT ASSIMILATION OF NITRATE BY BACILLUS FOLYMYXA

Abstract

Bacillus polymyxa did not grow in a medium containing nitrate as a sole nitrogen source if kept under anaerobic condition, although it grew in the same medium under aerobic condition. The bacteria grew aerobically or anaerobically in media containing nitrite or ammonium nitrogen. When both nitrate and nitrite were supplied in various combinations under anaerobic condition, cell yield at the stationary growth phase was limited only by the amount of nitrite and independent of the amount of nitrate added. Washed cells that had been grown aerobically in nitrate-containing media could reduce nitrate either aerobically or anaerobically when glucose was used as an electron donor. During the nitrate reduction, little or no nitrite accumulated. When the gas phase in cultures that were growing aerobically on nitrate was changed to anaerobic condition, cells continued to grow and nitrate was continued to be assimilated, but cellular activity of nitrate reductase distinctly decreased. These results show that oxygen is required, not for the reaction, but for the formation of assimilatory nitrate reductase system of B. polymyxa.