John L. Ingraham

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.

The Physiological Genetics of Denitrification in Pseudomonas

Interest in the fate of soil nitrates is shared by a number of scientific disciplines. This is reflected by the diversity of approaches to the study of nitrate metabolism. An important element in the nitrate budget of the soil is the competition between bacteria and plants for this important and often-limiting nutrient.