REDUCTION OF NITRATE WITH MOLECULAR HYDROGEN BY PROTEUS VULGARIS

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Abstract
Nitrate was reduced to nitrite with molecular Ho by both whole cells and cell-free extracts of P. vulgaris. With the system saturated with 0.02% nitrate, 1 mole of H2 is consumed for every mole of nitrate reduced. Nitrite is not reduced further even in the presence of benzyl viologen and no reduction of nitrate occurs in the absence of H2. Both nitrate and nitrite inhibit the deuterium exchange reaction 27%. The opt. pH is 6.8 and the system is relatively insensitive to change of pH. There is a short lag phase in reduction which is increased by O2 and decreased by H2- All O2 must be removed before nitrate can be reduced.