SHORT-TERM N2-15 INCORPORATION BY AZOBACTER.

Bulen, W. A. (Charles F. Kettering Research Laboratory, Yellow Springs, Ohio), J. R. LeComte, and H. E. Bales. Short-term N(2) (15)-incorporation by Azotobacter. J. Bacteriol. 85:666-670. 1963.-Short-term N(2) (15)-incorporation measurements were used to determine which of the growth requirements were necessary for nitrogen fixation by Azotobacter agilis (A. vinelandii). Normal cells required neither added iron nor molybdenum, but a marked stimulation by Na(+) and a minor stimulation by Mg(2+) were observed. The Na(+) stimulation was not accompanied by an increase in O(2) uptake. A lag period preceded the response of molybdenum-deficient cells to added Mo. In systems employing 10 and 20% O(2) with 10% N(2) (15) in the gas phase, O(2) appeared to be both required and inhibitory. These observations may be helpful in attempts to fractionate cell-free nitrogen-fixing systems from this aerobe.