We cloned a bacterial copper-containing nitrite reductase (NirK) homolog gene of Aspergillus oryzae (AonirK). Alignment showed that amino acid residues crucial for copper binding are conserved in the deduced sequence of the fungal protein. The recombinant protein exhibited distinct nitrite reductase activity, and its absorption and EPR spectra showed the presence of type 1 and type 2 copper ato...

Two sequencing batch reactors, one with the conventional anoxic and aerobic (AO) process and the other with the multiple AO process, were operated to examine characteristics of biological nitrogen removal, especially of the multiple AO process. The long-term operation showed that the total nitrogen removal percentage of the multiple AO reactor was 38.7% higher than that of the AO reactor. In th...

Bacterial response to nitric oxide (NO) is of major importance since NO is an obligatory intermediate of the nitrogen cycle. Transcriptional regulation of the dissimilatory nitric oxides metabolism in bacteria is diverse and involves FNR-like transcription factors HcpR, DNR, and NnrR; two-component systems NarXL and NarQP; NO-responsive activator NorR; and nitrite-sensitive repressor NsrR. Usin...

Hyphomicrobium spp. are commonly identified as major players in denitrification systems supplied with methanol as a carbon source. However, denitrifying Hyphomicrobium species are poorly characterized, and very few studies have provided information on the genetic and physiological aspects of denitrification in pure cultures of these bacteria. This is a comparative study of three denitrifying Hy...

The characteristics of anaerobic phosphorus release and anoxic phosphorus uptake were investigated in sequencing batch reactors using denitrifying phosphorus removing bacteria (DPB) sludge. The lab-scale experiments were accomplished under conditions of various nitrite concentrations (5.5, 9.5, and 15 mg/L) and mixed liquor suspended solids (MLSS) (1844, 3231, and 6730 mg/L). The results obtain...

An intensified biofilm-electrode reactor (IBER) was developed to treat nitrate-contaminated drinking water. Different running conditions were conducted to investigate the behavior of autotrophic denitrification (AD) and heterotrophic denitrification (HD) in the IBER. In AD process, the nitrate nitrogen coulomb-reduction rate was used to evaluate the performance of the reactor. The maximum NO(3)...

• No N 2 O accumulation was observed for Accumulibacter in the presence of multiple electron acceptors. Electron competition did not limit reduction nitrite or by Accumulibacter. Competibacter has truncated denitrification pathway. Denitrifying phosphorus removal is a cost and energy efficient treatment technology that relies on polyphosphate accumulating organisms (DPAOs) utilizing nitrate as ...

In this study granular sludge taken from a denitrifying upflow sludge reactor was characterized. Denitrification rates were determined in batch tests with and without external carbon source addition and pH microprofiles of the granules were studied. The microbial community structure was also determined. The results showed that denitrification without carbon source addition occurs; however, the ...

Anaerobic microorganisms play key roles in the biogeochemical cycling of methane and non-methane alkanes. To date, there appear to be at least three proposed mechanisms of anaerobic methane oxidation (AOM). The first pathway is mediated by consortia of archaeal anaerobic methane oxidizers and sulfate-reducing bacteria (SRB) via "reverse methanogenesis" and is catalyzed by a homolog of methyl-co...

Ammonia-oxidizing bacteria (AOB) remove intracellular nitrite to prevent its toxicity by a nitrifier denitrification pathway involving two denitrifying enzymes, nitrite reductase and nitric oxide reductase. Here, a Cu-containing nitrite reductase from Nitrosococcus oceani strain NS58, a gammaproteobacterial marine AOB, was expressed in Escherichia coli and purified to homogeneity. Sequence homo...