Aerobic and anaerobic nitrate and nitrite reduction in free-living cells of Bradyrhizobium sp. (Lupinus).
Induction, energy gain, effect on growth, and interaction of nitrate and nitrite reduction of Bradyrhizobium sp. (Lupinus) USDA 3045 were characterized. Both nitrate and nitrite were reduced in air, although nitrite reduction was insensitive to ammonium inhibition. Anaerobic reduction of both ions was shown to be linked with energy conservation. A dissimilatory ammonification process was detected, which has not been reported in rhizobia so far. Nevertheless, anaerobic conversion of nitrate to ammonium was lower than 40%, which suggests the presence of an additional, nitrite reductase of denitrifying type. Nitrite toxicity caused a non-linear relationship between biomass produced and >2 mM concentrations of each N oxyanion consumed. At > or =5 mM initial concentrations of nitrate, a stoichiometric nitrite accumulation occurred and nitrite remained in the medium. This suggests an inhibition of nitrite reductase activity by nitrate, presumably due to competition with nitrate reductase for electron donors. Lowering of growth temperature almost completely diminished nitrite accumulation and enabled consumption as high as 10 mM nitrate, which confirms such a conclusion.
Polcyn
Wladyslaw
W
Department of Plant Physiology, Faculty of Biology, A. Mickiewicz University, Al. Niepodleglości 14, 61-713 Poznań, Poland. polcyn@rose.man.poznan.pl
Luciński
Robert
R
D000332:Aerobiosis; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000378:metabolism; D020369:Bradyrhizobium / Q000254:growth & development / Q000378:metabolism*; D004790:Enzyme Induction; D009565:Nitrate Reductases / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009572:Nitrite Reductases / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology
D001426:Bacterial Proteins; D009566:Nitrates; D009573:Nitrites; D000644:Quaternary Ammonium Compounds; D009565:Nitrate Reductases; D009572:Nitrite Reductases