The reduction of nitrate to ammonium by a Clostridium sp. isolated from soil.
Cultures of Clostridium KDHS2 reduced 15NO3- to 15NH4+ with a concurrent increase in molar growth yield of 15.7% compared with fermentatively grown bacteria. The bacteria exhibited a Ks (NO3-) of 0.5 mM and reduced NO3- maximally at a rate of 0.1 mumol h(-1) mg dry wt)-1. A partially purified nitrate reductase was obtained which had a Km (NO3-) of 0.15 mM. The reduction of 13NO3- to 13NH4+ by resting bacteria was not inhibited by NH4+, glutamate, glutamine, methionine sulphoximine or azaserine. Glutamine synthetase affected neither the synthesis nor the activity of the NO3(-)-reducing enzymes. The results are consistent with the hypothesis that NO3- reduction to NH4+ in this Clostridium sp. is dissimilative. SO32-, but not SO42-, inhibited the reaction, apparently at the level of NO2- reduction.
D003013:Clostridium / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D007700:Kinetics; D009565:Nitrate Reductases / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D013447:Sulfites / Q000494:pharmacology
D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D013447:Sulfites; D009565:Nitrate Reductases; D005974:Glutamate-Ammonia Ligase