EFFECT OF MEDIUM COMPOSITION ON THE DENITRIFICATION OF NITRATE BY PARACOCCUS-DENITRIFICANS

The course of denitrification of nitrate in static cultures of Paracoc cus denitrificans was studied. Reduction of nitrate to gaseous nitroge n without accumulation of nitrite because of parallel and balanced act ivities of nitrate and nitrite reductases was observed in nutrient bro th. In minimal liquid cultures supplemented with either methanol, acet ate, or ethanol as a sole carbon source, substantial amounts of nitrit e (up to 70%) accumulated. The reduction in nitrite concentration bega n just after the transformation of nitrate to nitrite was completed. T he addition of some growth factors to minimal media shortened the bact erial biomass doubling time. A correlation coefficient of 0.71 between the doubling time and the amount of accumulated nitrite in cultures w as found. My results indicated that the type of denitrification carrie d out by P. denitrificans is not stable and depends on the nutritional composition of the culture medium.