Nitrate Reductase and Nitrous Oxide Production by Fusarium oxysporum 11dn1 Under Aerobic and Anaerobic Conditions

Abstract

The fungus Fusarium oxysporum 11dn1 was found to be able to grow and produce nitrous oxide on nitrate-containing medium in anaerobic conditions. The rate of nitrous oxide formation was three to six orders of magnitude lower than the rates of molecular nitrogen production by common denitrifying bacteria. Acetylene and ammonia did not affect the release of nitrous oxide release. 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 conditions led to a decline in nitrate reductase activity and stopped nitrous oxide production. The presence of two nitrate reductases was shown, which differed in molecular mass, location, temperature optima, and activity in nitrate- and ammonium-containing media. Two enzymes represent assimilatory and dissimilatory nitrate reductases, which are active in aerobic and anaerobic conditions, respectively.

Oxygen requirement for denitrification by the fungus Fusarium oxysporum

“…This is supported by the findings that the Nar mutants evolved more N 2 O than wild-type cells (Table 4); thus, assimilatory and dissimilatory types of metabolic NO 3 -reduction were simultaneously induced. This is consistent with a recent report by Kurakov et al (2000) showing that dissimilatory and assimilatory Nar are both present in denitrifying cells of F. oxysporum.…”

Soil Moisture and pH Control Relative Contributions of Fungi and Bacteria to N2O Production

“…A number of fungal isolates have shown N 2 O-producing activity in pure cultures [15][16][17][18][19][20][21][22]. Although fungal N 2 O production was found to be orders of magnitude lower than that of bacteria under pure culture conditions [23], direct soil measurements showed fungal dominance of N 2 O production [21,[24][25][26][27]. This is perhaps because fungi generally account for a significant portion of total soil microbial biomass.…”

The effect of oxygen on fatty acid composition of soil micromycetes

“…Fungal propagules on silica gel were directly inoculated into 100 mL flasks filled with 20 mL of sterile liquid medium containing (g L −1 of distilled water): glucose, 10.00; KH 2 PO 4 , 1.00; Na 2 HPO 4 , 0.43; KCl, 0.52; MgSO 4 , 0.52; NaNO 2 , 0.69; solution of trace elements, 1 mL (Kurakov et al, 2000). The effect of decreasing oxygen level on fungal isolates was assessed in three treatments for each isolate: Aerobic-cellulosic stopper; Microaerobic-butyl rubber stopper, screw cap, headspace atmosphere unchanged; Anaerobic-butyl rubber stopper, screw cap, headspace atmosphere replaced by argon.…”