Production of NO ₂ ^- and N ₂ O by Nitrifying Bacteria at Reduced Concentrations of Oxygen

Abstract

Pure cultures of the marine ammonium-oxidizing bacterium Nitrosomonas sp. were grown in the laboratory at oxygen partial pressures between 0.005 and 0.2 atm (0.18 to 7 mg/liter). Low oxygen conditions induced a marked decrease in the rate for production of N02 , from 3.6 x 1010 to 0.5 x 10`0 mmol of N02 per cell per day. In contrast, evolution of N20 increased from 1 x 10-12 to 4.3 x 10-12 mmol of N per cell per day. The yield of N20 relative to N02increased from 0.3% to nearly 10% (moles of N in N20 per mole of N02-) as the oxygen level was reduced, although bacterial growth rates changed by less than 30%. Nitrifying bacteria from the genera Nitrosomonas, Nitrosolobus, Nitrosospira, and Nitrosococcus exhibited similar yields of N20 at atmospheric oxygen levels. Nitriteoxidizing bacteria (Nitrobacter sp.) and the dinoflagellate Exuviaella sp. did not produce detectable quantities of N20 during growth. The results support the view that nitrification is an important source of N20 in the environment.

Processes Regulating Soil Emissions of NO and N^2O in a Seasonally Dry Tropical Forest

“…Sd) provides support for a biological reductive pathway for N 2 0 production. Furthermore, the amount ofN 2 0 produced by nitrifiers relative to N0 2 -and NO,-is known to increase as soil moisture increases (Goodroad and Keeney 1984) or as the partial pressure of oxygen (p0 2 ) decreases (Goreau et al 1980), which is consistent with a positive correlation between post-wetting soil moisture and N 2 0 flux ( Fig. 3a).…”

Phylogenetic analysis of nitric oxide reductase gene homologues from aerobic ammonia-oxidizing bacteria

“…The reason for our inability to amplify a norB product from Nitrosospira species, whether it is due to primer mismatch or absence of the gene is unknown at this time. Nitrosospira species are known to produce N 2 O with yields similar to Nitrosomonas species [46,47], although production of N 2 O by Nitrosospira briensis is less sensitive to C 2 H 2 and O 2 levels compared with N. europaea [48]. It is surprising, though, to have successfully amplified a norBlike sequence from N. oceani but not from the more closely related b-subdivision nitrifiers.…”

Aerobic and anaerobic ammonia oxidizing bacteria – competitors or natural partners?

“…This is in good agreement with recent studies that show that these microorganisms have a more versatile metabolism than previously assumed. Ammonia oxidizers can denitrify with ammonia as electron donor under oxygen-limited conditions [15,16] or with hydrogen or organic compounds under anoxic conditions [17]. Finally they can use N 2 O 4 as oxidant for ammonia oxidation under both oxic and anoxic conditions [18].…”