Genetics of Denitrification in Pseudomonas Aeruginosa and Stutzeri
Genetic studies on denitrifiers have been largely limited to Pseudomonas aeruginosa because of its well studied genetic systems of gene transfer—conjugative and transductional. Studies on this organism have identified and located a number of genes encoding the enzymes that mediate nitrate reduction including the assimilatory and dissimilatory nitrate and nitrite reductases. All of these are chromosomically located and none is contiguous with another. These studies also revealed the biochemical explanation for assimilatory and dissimilatory nitrate reduction being catalyzed by distinct enzyme: the dissimilatory enzyme cannot function in the presence of oxygen because electrons from the membrane-associated transport chain flow preferentially to it rather than nitrate.
In spite of its many advantages as an paradigm for physiological genetic studies on denitrification, its uniqueness among denitrifiers investigated so far in not being able to grow with N2O as sole oxidant severely limit its utility for investigations on the later steps of the denitrification pathway. Pseudomonas stutzeri grows well on exogenous N2O as sole oxidant, but its use in physiological genetic studies required the development of procedures for genetic exchange and manipulation. Procedures for genetic exchange by transformation, insertion mutagenesis, and mapping have been developed recently making this organism an excellent subject for future studies.
KeywordsNitrous Oxide Pseudomonas Aeruginosa Nitrate Reductase Anaerobic Growth Pseudomonas Stutzeri
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- Bryan, B.A., 1982, Cell yield and energy characterization of denitri-fication with Pseudomonas sutzeri and Pseudomonas aeruginosa, Ph.D. Thesis, University of California, Davis, U.S.A.Google Scholar
- Carlson, C.A., and Ingraham, J.L., 1983, Comparison of denitrification by Pseudomonas stutzeri Pseudomonas aeruginosa and Para-coccus denitrificans, Appl. Environ. Microbiol 44:1247.Google Scholar
- Carlson, C.A., Pierson, L.S., Rosen, J.J., and Ingraham, J.L., 1983, Pseudomonas stutzeri and related species undergo natural transformation, J. Bacteriol., 153: 93.Google Scholar
- Jeter, R.M., 1983, Pathways of nitrate reduction in pseudomonads: physiology and genetics, Ph.D. Thesis, University of California, Davis, U.S.A.Google Scholar
- Sias, S.R., and Ingraham, J.L., 1979, Isolation and analysis of mutants of Pseudomonas aeruginosa unable to assimilate nitrate, Arch. Microbiol 122:263.Google Scholar
- Sias, S.R., Stouthamer, A.H., and Ingraham, J.L., 1980, The assimilatory and dissimilatory nitrate reductases of Pseudomonas aeruginosa are encoded by different genes, J. Gen. Microbiol 118: 229.Google Scholar
- Stewart, V., 1982, Requirement for Fnr and NarL functions for nitrate reductase expression in Escherichia coli K12, J. Bacteriol., 151: 1320.Google Scholar