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The role of the nnR gene product in the response of Rhodobacter sphaeroides 2.4.1 to exogenous nitric oxide was analyzed. The nnR gene was subcloned and sequenced from the fragments taken from the pool of plasmids. Results of the study revealed that R. sphaeroides 2.4.1. carries nnR, the nor operon and the nnrS which are used for the denitrification of the bacterium. This indicate that products of nnrR and the genes flanking it are utilized when 2.4.1 is growing in the occurrence of denitrification.

The spatial heterogeneity in the distribution of denitrifying enzyme activity (DEA) was 3.5 times more in artificial denitrification activity zones than in bulk soil and the denitrifier biomass was 1-4 times more in activity zones. The potential heterogeneous distribution of denitrifying bacteria should be considered while measuring the denitrifying specific activity.

Denitrification of nitrate in static cultures of Paracoccus denitrificans was examined. Nitrate was reduced to a gaseous state without the aggregation of nitrite due to parallel and balanced functioning of nitrate and nitrite reductase in nutrient broth. Results proved that the manner of denitrification in Paracoccus denitrificans was not stable. This process is also dependent on the nutritional constitution of the culture medium.

The interactions between methylamine dehydrogenase (MADH) and two electron transfer proteins, amicyanin and cytochrome c-551i from Paracoccus denitrificans, are studied. The studies have shown that electron transfer from MADH to cytochrome c-551i has not involved a ternary complex but has occurred via a ping-pong mechanism in which amicyanin has used the same interface for the reactions with MADH and cytochrome c-551i.

The regulation of denitrification is examined in the model organism Paracoccus denitrificans during transition to anoxia both at pH 7 and when challenged with pHs ranging from 6 0t 7.5. The studies have shown that the inhibition has occurred during protein synthesis/assembly rather than transcription and have helped in understanding the regulation of the [N.sub.2]O redustase and the important role of pH in [N.sub.2]O emission.

The role of GlbN, a protein of the 2/2 hemoglobin lineage from cyanobacterium Synechococcus sp. PCC 7002, is studied. The studies have shown that GlbN protects cells from reactive nitrogen species that is encountered naturally during growth on nitrate or under denitrifying conditions.

The Methylomicrobium album ATCC 33003 and Methylocystis sp. strain ATCC 49242 in cultures with high nitrite levels and high ammonium levels were explored to study the effects of nitrite and ammonium on cultivated methanotrophic bacteria. M. album pure cultures and cocultures which consumed nitrite and produced nitrous oxide indicated the association between denitrification and nitrite tolerance.

The microbial community present in the produced waters from the Enermark field during nitrate injection is determined by denaturing gradient gel electrophoresis (DGGE) and the fate of the injected nitrate is determined by monitoring ammonium concentration in produced and injection waters. The results have shown that nitrate injected into an oil field to oxidize sulfide is reduced by denitrifying bacteria and that perhaps counterintuitively, nitrate injection has led to decreasing ammonium concentrations in produced waters.

Denitrification and artificial wastewater media was used to monitor denitrification activity of strain TR2 isolated from the aerobic denitrifying bacterium Pseudomonas stutzeri. The results demonstrated that some of the bacterial species such as strain TR2 has adopted a strategy for survival by preferring denitrification to oxygen respiration and the bacterium is also found to contain the potential to reduce [N.sub.2]O emissions when applied to sewage disposal fields.

A comparative study was conducted to understand the relationship between soil and vegetation factors and microbial community structure and function in restored and reference wetlands within a mitigation bank. Microbial functions was found to be influenced by composition of bacterial communities and soil fertility and the denitrifying populations could potential use for the development of predictive models for restoration of biogeochemical transformations and improve the success of wetland restoration efforts.

Isolation of five species of denitrifying bacteria from three phyla from subsurface sediments exposed to metal radionuclide and nitrate contamination as part of the U.S. Department of Energy's Oak Ridge Integrated Field Research Challenge (OR-IFRC) is described. The results demonstrated that a combination of cultivation and genomic and metagenomic data is essential to the in situ characterization of denitrifiers and that current PCR-based approaches are not suitable for deep coverage of denitrifiers.

Byline: Ning Li, Qian-fang Liao, Xue-cong Hu In order to model and minimise the effects of uncertainties in SCR (selective catalysis reduction) flue gas denitration, an approach of Type-II T-S fuzzy modelling based on data clustering is proposed in this paper. Type-II T-S fuzzy model, with the parameter fluctuation ranges in both antecedents and consequents, is an extension of Type-I T-S fuzzy model. For antecedents, the fluctuation ranges of fuzzy membership are computed by averaging the membership differences among similar data, and the Type-I fuzzy set can then be expanded to Type-II T-S fuzzy sets. For consequents, the fluctuation ranges of the data output sections are computed by averaging the output differences of the data with similar input sections, and the fluctuation bounds of the linear polynomial coefficients can then be identified by least square method, which means the crisp coefficients can be expanded to Type-I fuzzy sets. A simulation platform is set up to facilitate the research of SCR flue gas denitration process, based on the platform, the simulation results of SCR process are provided to certify that the proposed approach of Type-II T-S fuzzy modelling is superior to the existing approaches of Type-I T-S fuzzy modelling in terms of accuracy.

Geostatistical modeling to map spatial patterns were used to explore the distribution of the community structure, size, and activity of one functional group in N cycling, the denitrifiers, in relation to 23 soil parameters over a 44-ha farm divided into one organic and one integrated crop production system. The different community patterns along with the spatial distribution of the nirS/nirK abundance ratio suggested habitat selection on the nirS- and nirK-type denitrifiers and constituted a first step in identifying positions for denitrifiers at scales relevant to land management.

An rRNA-derived eukaryote clone library was constructed to identify the active protozoan phylotypes present in activated sludge and RNA-SIP was used to track carbon from bicarbonate and acetate into protozoa under ammonia-oxidizing and denitrifying conditions. The results from RNA-SIP analysis indicated that the peritrich ciliate Epistylis galea dominated the acquisition of carbon from bacteria with access to C[O.sub.2] under ammonia-oxidizing conditions, while no evidence was found for the specific grazing on acetate consumers under denitrifying conditions.

A study was conducted to determine the effects of red clover, soybean, and barley plant residues and of glucose on denitrifier abundance, denitrification gene mRNA levels, nitrous oxide ([N.sub.2]O) emissions, and denitrification rate quantified in anoxic soil microcosms for 72 h. Denitrification and respiration was found to increase in soil amended with organic carbon, including plant residues, compared to unamended soil.

The various effects of the changes taking place in the soil pH on the [N.sub.2]O and [N.sub.2] emissions and the activity of the denitrifier community are discussed. The nature of the denitification end products is shown to be completely determined by the pH of the soil.

Byline: M. Vieira, A.G. Brito, R. Nogueira This study aimed to investigate the effects of carbon availability and intermittent aeration on nitrogen removal in a Sequencing Batch Biofilm Reactor (SBBR). The percentage of nitrogen removal in the SBBRs operating with dump fill and slow fill with optimum intermittent aeration was quite similar, 75.7% and 69.2%, respectively, indicating that intermittent aeration allowed a considerable energy saving without compromising significantly nitrogen removal. Accumulation of storage polymers by heterotrophic bacteria was only observed in the dump fill mode of operation. FISH analyses of the biofilm indicated that ammonia-oxidisers belonged to the beta-subclass Proteobacteria and nitrite-oxidisers were affiliated with the genus Nitrospira.

The denitrifier community of an nitrous oxide ([N.sub.2]O)-emitting fen (pH 4.7 to 5.2) is examined. The studies have shown that the regional fen has harbored novel, highly diverse, acid-tolerant denitrifier communities that are capable of complete denitrification and consumption of atmospheric [N.sub.2]O at in situ pH.

The portion of the nirK denitrifying community that is active and has contributed to denitrification under conditions in a potato crop field is studied. The results have shown that the soil denitrifier populations bearing nirK genes are not all contributing to denitrification and that the denitrifying populations that are active are abundant and ubiquitous nirK-bearing denitrifiers.

A comparative 16S rRNA gene analysis is conducted to explain the response of the microbial populations to denitrification, including the different conditions observed in the rice paddy soil. The various potential key players involved in the nitrate respiration and denitrification processes are also identified.

The development of a stable isopropyl-[beta]-D-thiogalactopyranoside (IPTG)-inducible-expression plasmid, pIND4 which permitted graduated levels of protein expression in the alphaproteobacteria Rhodobacter sphaeroides and Paracoccus denitrificans is described. The plasmid pIND4 showed kanamycin resistance and combined the stable replicon of pMG160 with the [lacI.sup.q] gene from pYanni3 and the lac promoter, [P.sub.A1/04/03] from pJBA24.

The criteria for standardizing operational taxonomic units (OUT) assignment of environmental narG and nosZ sequences is resolved and the impact of horizontal gene transfer on narG is examined. The studies have shown that genus-level tree topologies of narG and nosZ are similar to those of the corresponding 16S rRNA genes.

The denitrifying properties of Ochrobactrum anthropi are examined, where the strain YD50.2 has denitrified high levels of N[O.sub.2.sup.-] to dinitrogen under anaerobic conditions. The results have shown that Ochrobactrum anthropi YD50.2 has mechanisms that have produced tolerance to reactive nitrogen species (RNS).

Byline: Xiang Hu, Yanfang Shi, Jianlong Wang In this paper, the bio-activity of activated sludge was investigated using Oxygen Uptake Rate (OUR) as an indicator. The activity of ammonium oxidation and COD removal of both attached- and suspended-growth sludge was determined under different temperature and organic loading rates. The experimental results indicated that at 5[degrees]C, the nitrification activity was about 60% of that at 18[degrees]C. The nitrification activity of attached sludge was 20-30% lower in comparison with suspended sludge. The denitrification rate of sludge in zones I and II was 0.44 mg NO3−/g MLSS•h and 0.63 mg NO3−/g MLSS•h, respectively, which revealed that the denitrification activity of sludge-II was higher compared with sludge-I, the results also indicated that the accumulation of nitrite was very low.

A special variant of whole-cell hybridization termed recognition of individual genes-fluorescence in situ hybridization (RING-FISH) is used to understand the phylogeny of the organisms from which the nitrite reductase (nirK) gene originated. The results obtained from RING-FISH provide insight into the phylogenetic classification of nirK-type denitrifiers and the phylogeny and function of denitrifying microorganisms in the environment.

A study is conducted to examine the factors such as environmental conditions, nutrient availability and levels of pollutants on denitrifying microbial community composition and denitrification enzyme activities (DEA) at a California salt marsh with high nutrient loading. The community composition and DEA are found to be highly variable within the dynamic salt marsh system, but each is strongly affected by elevation and carbon content as well as by selected metals.

A research study is conducted to measure nitric oxide reductase (cnorB) gene expression in Pseudomonas mandelii and [N.sub.2]O emissions from denitrification with and without a nitrate substrate. The results demonstrated that P. mandelii cnorB gene expression is induced when nitrate is present in the medium and accumulation of [N.sub.2]O has indicated the production of cNorB enzyme.

The physiological, genetic, and biochemical experiments are performed to detect genes encoding monooxygenase and dioxygenase enzymes potentially involved in benzene degradation in strain BC. The results revealed that oxygen formed during the dismutation of chlorite might be used as terminal electron acceptor in strain BC as well as to attack molecules by means of oxygenases.

Several studies are done for investigating the cytochrome c oxidase reaction with oxygen in a mutant with a blocked D-pathway of proton transfer (D124N, Paracoccus denitrificans numbering).

The thermal denitrogenation of 3-carbomethoxysubstituted 4-spirocyclopropane-1-pyrazolines is studied. Computational studies have explained the notable effects of substituents on the denitrogenation mechanism, in which nonstatistical dynamics have played a vital role in controlling the product selectivity in the denitrogenation reactions.

Study is conducted to reveal the denitrification ability of candidate accumulibacter phosphates organism. The results of this study material can be adapted to other uncultured bacteria.

The inhibitory effects of acetylene, methanol and allyithiourea (ATU) on anammox and denitrification activities in marine sediments re examined. No marked effects on the rates of anammox and denitrification were found in ATU.

Measurements of rates of canonical, that is, heterotrophic, water-column denitrification were performed by [super 15]N incubation techniques at a number of coastal and open ocean stations in the Arabian Sea. Nitrogen excess gas measurements were found to predict a larger nitrogen anomaly than estimated by classical stoichiometric methods.

An evolutionary algorithm is applied to study the complex interactions between medium parameters and their effects on the isolation of denitrifying bacteria, both in number and in diversity. One hundred ninety-nine denitrifiers are isolated, the majority of which belonged to the Betaproteobacteria (50.4%) and the Alphaproteobacteria (36.8%).

Two transmembrane proteins were tentatively classified as NarK1and NarK2 in the Pseudonomas genome project and hypothesized to play an important physiological role in the nitrate/nitrite transport in Pseudonomas aeruginosa. It was observed that Pseudonomas aeruginosa needed only NarK2 as a nitrate/nitrite transporter, under denitrifying conditions.

A study is conducted to demonstrate that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3(super -) reduction from denitrification to dissimilatory NO3(super -) reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized H2S with NO3(super -) and transported S(super 0) to the sediment surface for aerobic oxidation.

The process of denitrification, which is the initial step in the reduction of nitrate to dinitrogen, is catalyzed by the respiratory nitric oxide reductase (NOR). The transfer of protons to the catalytic site, during the reduction of nitrate to dinitrogen, is mainly due to the presence of amino acid residue.

The internal transformations of nitrogen in terrestrial ecosystems exert strong controls over nitrogen availability to net primary productivity, nitrate leaching into groundwater, and emissions of nitrogen-based greenhouse gas. Here we report a reductive pathway for nitrogen cycling in upland tropical forest soils that decreases the amount of nitrate susceptible to leaching and denitrification, thus conserving nitrogen in the ecosystem. Using [sup.15]N tracers we measured rates of dissimilatory nitrate reduction to ammonium (DNRA) in upland humid tropical forest soils averaging ~0.6 [micro] g [multiplied by] [g.sup.-1] [multiplied by] [d.sup.-1]. Rates of DNRA were three times greater than the combined [N.sub.2]O and [N.sub.2] fluxes from nitrification and denitrification and accounted for 75% of the turnover of the nitrate pool. To determine the relative importance of ambient C, [O.sub.2], and [NO.sub.3] concentrations on rates of DNRA, we estimated rates of DNRA in laboratory assays using soils from three tropical forests (cloud forest, palm forest, and wet tropical forest) that differed in ambient C and [O.sub.2] concentrations. Rates of DNRA measured in laboratory assays ranged from 0.5 to 9 [micro] g [multiplied by] [g.sup.-1] [multiplied by] [d.sup.-1] in soils from the three different forests and appeared to be primarily limited by the availability of [NO.sub.3], as opposed to C or [O.sub.2]. Tests of sterile soils indicated that the dominant reductive pathway for both [NO.sub.2] and [NO.sub.3] was biotic and not abiotic. Because [NH.sub.4] is the form of N generally favored for assimilation by plants and microbes, and [NO.sub.3] is easily lost from the ecosystem, the rapid and direct transformation of [NO.sub.3] to[NH.sub.4] via DNRA has the potential to play an important role in ecosystem N conservation. Key words: denitrification; dissimilatory nitrate reduction to ammonium (DNRA); [sup.15]N; nitrogen cycling; nitrous oxide; tropics; upland tropical forest soils.

This study investigates the denitrification/phosphate uptake and denitrification/phosphate release characteristics among denitrifying phosphate accumulating organisms (DNPAO), denitrifier, and nondenitrifying phosphate accumulating organisms (non-DNPAO) in a biological nutrient removal process named TNCU-I, using a series of anoxic batch experiments with and without added acetate under high/low intracellular polymer conditions. The results showed 47% phosphate uptake in the anoxic tank of the TNCU-I process. Additionally, due to the combined attribution of denitrifier and DNPAO, the experiments with both added acetate and phosphate produced higher denitrification rates than experiments with only acetate added. Furthermore, DNPAO contributed 42% of the denitrification reaction. The sludge exhibited simultaneous phosphate uptake and release under anoxic conditions when acetate was added. When no acetate was added, the specific phosphate uptake rate for the high intracellular polymer level was higher than that found at the low intracellular polymer level. Moreover, the phosphate uptake rate of non-DNPAO was observed to be 2.46 times greater than that of the DNPAO. The phosphate uptake per unit polyhydroxyalkanoates (PHA) consumption ([[Gamma].sub.[[PO.sub.4]/PHA]]) for the non-DNPAO was 1.08 times greater than that of DNPAO. Thus, this study demonstrates that the utilization efficiency of PHA by non-DNPAO is not significantly different with the utilization efficiency of PHA by DNPAO.

Laboratory experiments were conducted to characterize the performance of an immobilized-cell denitrification process treating nitrate-contaminated groundwater and to provide supporting data for the validation of a quasi-steady state model based on half-order reaction kinetics. The treatment process consists of laboratory-scale, plug-flow reactors packed with biocatalyst particles. Pseudomonas denitrificans (American Type Culture Collection 13867), a heterotrophic denitrifier, was cultured and immobilized in calcium alginate particles. Ethanol was used as the source of organic carbon. Thirty concentration profiles were obtained at four levels of nitrate concentration and at three ranges of flow rate. An analysis of the nitrate and nitrite concentration profiles suggested that a half-order reaction rate model could be used to describe the reduction of both nitrate and nitrite. The half-order reaction rate constants for nitrate and nitrite reduction were dependent on the age of the biocatalyst particles and the nitrate loading history. The validity of the half-order denitrification model was satisfactorily tested with experimental data. As illustrated by preliminary calculations, the immobilized-cell denitrification process is feasible for practical applications, particularly for small drinking water systems.