SHORT-TERM N 2 15 -INCORPORATION BY AZOTOBACTER

Bulen , W. A. (Charles F. Kettering Research Laboratory, Yellow Springs, Ohio), J. R.LeComte, and H. E. Bales . Short-term N2 15 -incorporation byAzotobacter . J. Bacteriol.85: 666–670. 1963.—Short-term N2 15 -incorporation measurements were used to determine which of the growth requirements were necessary for nitrogen fixation byAzotobacter agilis (A. vinelandii ). Normal cells required neither added iron nor molybdenum, but a marked stimulation by Na+ and a minor stimulation by Mg2+ were observed. The Na+ stimulation was not accompanied by an increase in O2 uptake. A lag period preceded the response of molybdenum-deficient cells to added Mo. In systems employing 10 and 20% O2 with 10% N2 15 in the gas phase, O2 appeared to be both required and inhibitory. These observations may be helpful in attempts to fractionate cell-free nitrogen-fixing systems from this aerobe.