Although methanol is a widely employed carbon source for denitrification, relatively little is known on the abundance and diversity of methylotrophic bacteria in activated sludge. The primary aim of this study was to specifically identify bacteria that metabolized methanol in a sequencing batch denitrifying reactor (SBDR), using a novel technique, stable isotope probing (SIP) of 13C labeled DNA...

Ammonia-oxidizing bacteria (AOB) can use oxygen and nitrite as electron acceptors. Nitrite reduction by Nitrosomonas is observed under three conditions: (i) hydrogen-dependent denitrification, (ii) anoxic ammonia oxidation with nitrogen dioxide (NO(2)) and (iii) NO(x)-induced aerobic ammonia oxidation. NO(x) molecules play an important role in the conversion of ammonia and nitrite by AOB. Absen...

Peatlands cover more than 30% of the Finnish land area and impact N2O fluxes. Denitrifiers release N2O as an intermediate or end product. In situ N2O emissions of a near pH neutral pristine fen soil in Finnish Lapland were marginal during gas chamber measurements. However, nitrate and ammonium fertilization significantly stimulated in situ N2O emissions. Stimulation with nitrate was stronger th...

Fixed nitrogen (N) removal from estuaries via coupled nitrification–denitrification plays a significant role in the global N cycle and the biogeochemistry of individual estuaries. Much of our understanding of these processes is drawn from temperate estuaries, yet tropical and subtropical estuaries may respond differently to N inputs. I tested the hypothesis that nitrification is limited within ...

Nitrous oxide (N2O) is produced in the lower Seine river at 40 to 60 kg N-N2O d–1, in a section greatly affected by effluents from the Achères Wastewater treatment plant (WWTP). Because water column denitrification is weak in this sector, we hypothesized that N2O could be produced by the nitrifier-denitrification process. To understand the controls of N2O emission, nitrifying bacterial cultures...

Most denitrifying bacteria reduce nitrate to the inert gases nitrous oxide or nitrogen. A remarkable exception to this is Rhizobium sullae strain HCNT1, which catalyses only a single step in the denitrification pathway, the reduction of nitrite to the reactive molecule nitric oxide. Further study demonstrated that HCNT1 does not encode the genes for NO reductase. Prolonged incubation of HCNT1 u...

The onset and cessation of the synthesis of denitrification enzymes of Pseudomonas stutzeri were investigated by using continuous culture and defined dissolved oxygen levels covering the full range of transition from air saturation to complete anaerobiosis. Expression of nitrate reductase, nitrite reductase (cytochrome cd1), and N2O reductase was controlled by discrete oxygen levels and by the ...

It is generally assumed that during denitrification bacteria oxidize organic substances completely to carbon dioxide concomitant with the reduction of nitrate or nitrite to nitrogen and nitrous oxide. This assumption is based upon the early experiments of Gayon and Dupetit (1886) which demonstrated that the ratio of carbon dioxide to nitrogen in denitrifying cultures corresponded to the theoret...

Step-feeding strategies have been extensively studied and comprehensively analyzed in this study for a four-stage alum sludge-based tidal flow constructed wetlands (AlS-TFCWs) system. Enhanced total nitrogen removal of 83% is achieved under high nitrogen loading rate of 19.1 g N/m(2)d. The key issues towards the success of a significant nitrogen removal in step-feeding TFCWs are the bed resting...