Carbon monoxide inhibition of nitrogen fixation by Azotobacter

Abstract

CO inhibition of nitrogen fixation by Azotobacter vinelandii has been established. Definite inhibition is observed when the CO concentration is 0.1-0.2%; it increases with the pCO until at 0.5-0.6% fixation is almost completely suppressed. This inhibition is comparable with that of inoculated red clover plants, but the quantity of CO required is about 10 times greater than for the symbiotic system. In the range of CO concentration inhibitory for nitrogen fixation by azotobacter little consistent effect is noted on the assimilation of combined nitrogen, thereby establishing the specificity of the inhibition for nitrogen fixation. Certain of the findings were made possible only because rate as well as extent of fixation was measured and because two supplementary techniques - a micro and a macro - were used. The advantage and necessity of such type of experimental variation are discussed. 7 references, 6 figures, 3 tables.