Pseudomonas stutzeri, nitrite reductase

Gruntzig, V., Nold, S. C., Zhou, J. Z., and Tiedje, J. M. (2001). Pseudomonas stutzeri nitrite reductase gene abundance in environmental samples measured by real-time PCR. Appl. Environ. Microbiol. 67, 760-768. 

A strain of Escherichia coli produces a naphthotriazole from 2,3-diaminonaphthalene and nitrite that is formed from nitrate by the action of nitrate reductase. The initial product is NO, which is converted by reactions with oxygen into the active nitrosylating agent that reacts chemically with the amine (Ji and Hollocher 1988). A comparable reaction may plausibly account for the formation of dimethylnitrosamine by Pseudomonas stutzeri during growth with dimethylamine in the presence of nitrite (Mills and Alexander 1976) (Figure 2.2f). 

Although the pathway of Eq. (1) is now based on much evidence (Section 111) and is unambiguous in the case of at least one bacterium [Pseudomonas stutzeri strain Zobell (f. sp. P. perfectomarina)], there have been alternative hypothesis. One hypothesis, advanced by the Hollocher group (Garber and Hollocher, 1981 St. John and Hollocher, 1977), considered NO as a likely intermediate, but one that remained at least partly enzyme-bound and was not entirely free to diffuse. This view was based on the outcome of certain kinetic and isotope experiments which can be summarized as follows. When denitrifying bacteria were challenged simultaneously with [ N]nitrite and ordinary NO, the cells reduced both compounds concomitantly to N2 (or to N2O in the presence of acetylene which is a specific inhibitor (Balderston et al., 1976 Yoshinari and Knowles, 1976) of nitrous oxide reductase). In the process, little NO was generally detected in the gas phase pool of NO and there was relatively little isotopically mixed N2O formed. That is, most of the N and N reduced to NjO appeared as N2O... 

Glockner, A. B., Jiingst, A., and Zumft, W. G. (1993). Copper-containing nitrite reductase from Pseudomonas aureofaciens is functional in a mutationally cytochrome cd,-free background (NirS ) of Pseudomonas stutzeri. Arch. Microbiol. 160, 18-26. 

Jiingst, A., Braun, C., and Zumft, W. G. (1991a). Close linkage in Pseudomonas stutzeri of the structural genes for respiratory nitrite reductase and nitrous oxide reductase, and other essential genes for denitrification. Mol. Gen. Genet. 225, 241-248. 

Weeg-Aerssens, E., Wu, W., Ye, R. W., Tiedje, J. M., and Chang, C. K. (1991). Purification of cytochrome cdj nitrite reductase from Pseudomonas stutzeri JM 300 and reconstitution with native and synthetic heme di- ]. Biol. Chem. 266, 7496-7502. 

Wilson EK, Bellelli A, Cutruzzola F, Zumft WG, Gutierrez A, Scrutton NS. Kinetics of CO binding and CO photodissociation in Pseudomonas stutzeri cd2 nitrite reductase probing the role of extended N-termini in fast structural relaxation upon CO photodissociation. Biochem J 2001 355 39 13. 

Cheesman, M., Ferguson, S. J., Moir, J. W. B., Richardson, D. J., Zumft, W. G., and Thomson, A. J., 1997, Two enzymes with a common function but different heme ligands. The optical and magnetic properties of the heme groups in the oxidised forms of nitrite reductase, cytochrome cdi, from Pseudomonas stutzeri and Thiosphaera pantotropha. Biochemistry 36 16267916276. 

It is also possible to use antibody based approaches to assay the accumulation of enzymes involved in denitrification pathways in environmental samples. Ward and Cockroft (1993) developed antisera to nitrite reductase from a marine Pseudomonas stutzeri isolate, and assayed sediment, water column and microbial mat samples. The antibody identified nitrite reductase in mat samples and was more specific than a DNA probe designed against the same species (Ward and Cockroft, 1993). JVIore recently, other strains of denitrifiers have been isolated from both sediment and water column samples. Sequence information regarding the denitrifying genes should prove invaluable for future refinement of both sequence based approaches and the development of additional antibodies to denitrifiers important in the marine environment. 

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