The Effect of Molybdenum upon the Nitrogen Metabolism of Anabaena cylindrica

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Abstract
Molybdenum-deficiency in Anabaena cylindrica results in a decrease of all the organic nitrogen fractions determined analytically with the exception of amide which occurs at approximately the same concentration irrespective of the molybdenum status. Molybdenum-rich, nitrogen-starved cells assimilate nitrate to protein rapidly in the dark; similarly treated molybdenum-deficient cells rapidly reduce nitrate to ammonia and amide, but the further synthesis to peptides and proteins proceeds very slowly. The rate of endogenous respiration is higher in deficient than in normal cells, but the rate of glycolysis is lower. No period of adaptation is required, after the addition of molybdenum to deficient cells, before normal nitrogen metabolism commences. Glucose, acetate, fumarate, succinate, and citrate are respired by normal and deficient cells in the dark. Acetate has no effect on nitrate reduction, glucose stimulates the reduction for a short period, while fumarate (and probably succinate) and, somewhat less efficiently, citrate, stimulate reduction in both normal and deficient cells and enable the deficient cells to assimilate nitrate completely to protein. It would seem that, in the absence of molybdenum, there is an insufficient supply of hydrogen and/or energy donors to permit complete nitrate assimilation.