Agricultural systems that receive high or low organic matter (OM) inputs would be expected to differ in soil nitrogen (N) transformation rates and fates of ammonium (NH4 þ) and nitrate (NO3 ). To compare NH4 þ availability, competition between nitrifiers and heterotrophic microorganisms for NH4 þ, and microbial NO3 2 assimilation in an organic vs. a conventional irrigated cropping system in the...

We examine and discuss literature targeted at identifying "active" subpopulations of soil microbial communities with regard to the factors that affect the balance between mineralization and immobilization/assimilation of N. Whereas a large fraction (≥50%) of soil microbial biomass can immediately respire exogenous substrates, it remains unclear what percentage of both bacterial and fungal popul...

The process of nitrate reduction via nitrite controls the fate and bioavailability of mineral nitrogen within ecosystems; i.e., whether it is retained as ammonium (ammonification) or lost as nitrous oxide or dinitrogen (denitrification). Here, we present experimental evidence for a novel pathway of microbial nitrate reduction, the reverse hydroxylamine:ubiquinone reductase module (reverse-HURM)...

Although considerable knowledge exists on the impact of crop residues soil N availability, information about their nitrification specifically is lacking. The unique physiologies ammonia oxidizing archaea (AOA) suggests activities might respond differently to residue amendment compared bacteria (AOB). An incubation study was conducted two widely distributed Oregon agricultural silt loam soils Wa...

pH has been recognized as one of the key environmental parameters with significant impacts on the nitrogen cycle in the environment. In this study, the effects of pH on NO3-/NO2- fate and N2O emission were examined with Shewanella loihica strain PV-4, an organism with complete denitrification and respiratory ammonification pathways. Strain PV-4 was incubated at varying pH with lactate as the el...

The moisture-temperature regime influences the nitrogen status of soil and microbiological processes transformation forms. Therefore, we assumed that ongoing climate change may affect emission nitrous oxide N2O, which is formed in course forms one most aggressive greenhouse gases determine global warming potential. To test this hypothesis make a quantitative assessment impact on N2O emissions f...

During anaerobic nitrate respiration Bacillus subtilis reduces nitrate via nitrite to ammonia. No denitrification products were observed. B. subtilis wild-type cells and a nitrate reductase mutant grew anaerobically with nitrite as an electron acceptor. Oxygen-sensitive dissimilatory nitrite reductase activity was demonstrated in cell extracts prepared from both strains with benzyl viologen as ...