Denitrifying

Figure 3 Partitioning of losses of nitrogen fertilizer between denitrifieation and leaehing in 13 experiments. (Taken from Addiseott and Powlson, with permission of Cambridge University Press.)...

Denitriermittel, n. denitrating agent, Denitrierung, /. denitration, denitrifizieren, v.t. denitrify,... 

Heme d,6 another isobacteriochlorin, occurs as one of two cofactors in the reductase cytochrome cdj which mediates the nitrite reduction to nitrogen monoxide (NO) and from there to dinitrogen oxide (N20) in denitrifying bacteria.7... 

Assimilatory denitrifiers reduce nitrate to the amino acid level where it is incorporated into protein. Many plants and bacteria can do this and, therefore, use nitrate as a nitrogen source. 

Additional removal of BOD5 and T-N could be obtained at the anaerobic/anoxic tank of the constructed wetland. About 57 % of the ranaining BOD5 was removed at the anaerobic/anoxic tank. More than 74 % of the remaining T-N was denitrified, and the average concentration of T-N at the final effluent was 6.9 mg/L. The maximum available capacity for nutrient uptake in plants was far less (of the order of 5 %) than the loading rate of nutrients to the constructed wetland. 

Phenol is an important intermediate in the anaerobic degradation of many complex and simple aromatic compounds. Tschech and Fuchs proposed that the carboxylation of phenol to 4-hydroxybenzoate is the first step in the degradation of phenol under denitrifying conditions. However, 4-hydroxybenzoate is not detected in the cultures or cell extracts of the denitrifying Pseudomonas species in the presence of CO2 and phenol, but it is detected if phenol is replaced by phenolphosphate. In contrast, 4-hydroxybenzoate is readily detected as an intermediate of phenol degradation in the iron-reducing bacterium GS-15, and 4-hydroxybenzoate may prove to be a common intermediate in the anaerobic transformation. Thus, in anaerobic degradation of phenolic compounds, it has been postulated that carboxylation reactions may play important roles. 

A taxonomic note there have been substantial developments in the taxonomy of pseudomonads, and many new genera have been proposed including, for example, Sphingomonas, Comamonas, and Variovorax, while denitrifying organisms described as pseudomonads have been referred to the general Thauera and Azoarcus (Anders et al. 1995). 

Anders H-J, A Kaetzke, P Kampfer, W Ludwig, G Fuchs (1995) Taxonomic position of aromatic-degrading denitrifying pseudomonad strains K 172 and KB 740, and their description as new members of the genera Thauera, as Thauera aromatica sp. nov., and Azoarcus, as Azoarcus evansii sp. nov., respectively, members of the beta subclass of the Protobacteria. Int J Syst Bacterial 45 327-333. 

Rontani J-F, MJ Gilewicz, VD Micgotey, TL Zheng, PC Bonin, J-C Bertrand (1997) Aerobic and anaerobic metabolism of 6,10,14-trimethylpentadecan-2-one by a denitrifying bacterium isolated from marine sediments. Appl Environ Microbiol 63 636-643. 

Altenschmidt U, G Fucbs (1991) Anaerobic degradation of toluene in denitrifying Pseudomonas sp. indication for toluene metbylbydroxylation and benzoyl-CoA as central aromatic intermediate. Arch Microbiol 156 152-158. 

Criddle CS, JT DeWitt, D Grbic-Galic, PL McCarty (1990) Transformation of carbon tetrachloride by Pseudomonas sp strain KC under denitrifying conditions. Appl Environ Microbiol 56 3240-3246. 

Evans DT Mang, KS Kim, LY Young (1991a) Anaerobic degradation of toluene by a denitrifying bacterium. Appl Environ Microbiol 57 1139-1145. 

Evans PJ, DT Mang, LY Young (1991b) Degradation of toluene and m-xylene and transformation of o-xylene by denitrifying enrichment cultures. Appl Environ Microbiol 57 450-454. 

Harder J, C Probian (1997) Anaerobic mineralization of cholesterol by a novel type of denitrifying bacterium. Arch Microbiol 167 269-274. 

Nozawa T, Y Maruyama (1988) Anaerobic metabolism of phthalate and other aromatic compounds by a denitrifying bacterium. J Bacteriol 170 5778-5784. 

Taylor BF, MJ Heeb (1972) The anaerobic degradation of aromatic compounds by a denitrifying bacterium. Radioisotope and mutant studies. Arch Microbiol 83 165-171. 

Wolterink AFWM, AB Jonker, SWM Kengen, AIM Stams (2002) Pseudomonas chloritidismutans sp. nov., a non-denitrifying chlorate-reducing bacterium. Int J Syst Evol Microbiol 52 2183-2190. 

Wolterink AFWM, E Schiltz, P-L Hagedoorn, WR Hagen, SWM Kengen, AIM Stams (2003) Characterization of the chlorate reductase from Pseudomonas chloritidismutans. J Bacterial 185 3210-3213. Ziegler K, K Braun, A Bdckler, G Fuchs (1987) Studies on the anaerobic degradation of benzoic acid and 2-aminobenzoic acid by a denitrifying Pseudomonas strain. Arch Microbiol 149 62-69. 

Breese K, G Fuchs (1998) 4-hydroxybenzoyl-CoA reductase (dehydroxylating) from the denitrifying bacterium Thauera aromatica prosthetic groups, electron donor, and genes of a member of the molybdenum-flavin-iron-sulfur proteins. Eur J Biochem 251 916-923. 

Thauera sp. strain DNT-1 is able to degrade toluene under aerobic conditions mediated by a dioxygenase, and under denitrifying conditions in the absence of oxygen by the anaerobic benzylsuccinate pathway (Shinoda et al. 2004). Whereas the tod genes were induced under aerobic conditions, the bss genes were induced under both aerobic and anaerobic conditions. 

Shinoda Y, Y Sakai, H Uenishi, Y Uchihashi, A Hiraishi, H Yukawa, H Yurimoto, N Kato (2004) Aerobic and anaerobic toluene degradation by a newly isolated denitrifying bacterium, Thauera sp. strain DNT-1. Appl Environ Microbiol 70 1385-1392. 

These results may be viewed in the wider context of interactions between potential ligands of multifunctional xenobiotics and metal cations in aquatic environments and the subtle effects of the oxidation level of cations such as Fe. The Fe status of a bacterial culture has an important influence on synthesis of the redox systems of the cell since many of the electron transport proteins contain Fe. This is not generally evaluated systematically, although the degradation of tetrachloromethane by a strain of Pseudomonas sp. under denitrifying conditions clearly illustrated the adverse effect of Fe on the biotransformation of the substrate (Lewis and Crawford 1993 Tatara et al. 1993). This possibility should therefore be taken into account in the application of such organisms to bioremediation programs. 

The biodegradation of acenaphthene and naphthalene under denitrifying conditions was examined in soil-water slurries (Mihelcic and Luthy 1988), though in this case only analyses for the concentrations of the initial substrates were carried out. 

It has been shown that pure cultures of bacteria under anaerobic denitrifying conditions may produce benzylsuccinate as a metabolite of toluene (Evans et al. 1992 Migaud et al. 1996 Beller et al. 1996). Demonstration of this and the corresponding methylbenzyl succinates from xylenes has been used to demonstrate metabolism of toluene and xylene in an anaerobic aquifer (Beller et al. 1995, 2002). 

Lewis TA, RL Crawford (1993) Physiological factors affecting carbon tetrachloride dehalogenation by the denitrifying bacterium Pseudomonas sp. strain KC. Appl Environ Microbiol 59 1635-1641. 

Gallus C, B Schink (1994) Anaerobic degradation of pimelate by newly isolated denitrifying bacteria. Microbiology (UK) 140 409-416. 

Kniemeyer O, C Probian, R Rossello-Mora, J Harder (1999) Anaerobic mineralization of quaternary carbon atoms isolation of denitrifying bacteria on dimethylmalonate. Appl Environ Microbiol 65 3319-3324. 

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