Nitrate reductase and nitrous oxide production by Fusarium oxysporum 11dn1under aerobic and anaerobic conditions

The fungus Fusarium oxysporum 11dn1 was found to be able to grow and produc e nitrous oxide on nitrate-containing medium in anaerobic conditions. The r ate of nitrous oxide formation was three to six orders of magnitude lower t han the rates of molecular nitrogen production by common denitrifying bacte ria. Acetylene and ammonia did not affect the release of nitrous oxide rele ase. It was shown that under anaerobic conditions fast increase of nitrate reductase activity occurred, caused by the synthesis of enzyme de novo and protein dephosphorylation. Reverse transfer of the mycelium to aerobic cond itions led to a decline in nitrate reductase activity and stopped nitrous o xide production. The presence of two nitrate reductases was shown, which di ffered in molecular mass, location, temperature optima, and activity in nit rate- and ammonium-containing media. Two enzymes represent assimilatory and dissimilatory nitrate reductases, which are active in aerobic and anaerobi c conditions, respectively.