THE INFLUENCE OF FIXED NITROGEN ON AZOTOBACTER

Publisher Website
Google Scholar
Abstract
The equilibrium concentration of rapidly available fixed N in the culture medium required to inhibit N fixation by Azotobacter is 0.5 mg. per 100 cc. The rate of growth as a function of concentration of rapidly available fixed N passes through a maximum at 0.5-1.0 mg. per 100 cc, falling off sharply at lower, but much less rapidly at higher, concentrations. The efficiency of growth in fixed N increases with rate of growth. Hence, although increases in rates of respiration may be used as a qualitative measure of amounts of growth occurring simultaneously, the ratio, growth: respiration rate increase, increases rapidly with rate of growth, which in turn may depend on pressure of N gas, concentration of fixed N, presence of humic acid, O concentration, age of inoculum, and time. The % composition of N in the dry matter of the cells varies little, whether the N supply is chiefly free or fixed. Fixation seems to be a function resorted to only in absence of sufficiently available fixed N. The various physiological functions of respiration, growth, efficiency, etc., of Azotobacter in free and fixed N is quite similar; hence no conclusion can be drawn concerning the chemical mechanism of N fixation.

This publication has 1 reference indexed in Scilit: