Denitrification

The production of gaseous nitrogen by microbial reduction of nitrogenous oxides is known as biological denitrification. Bacteria are the only organisms that have the physiological property of denitrification. A mechanism other than denitrification also seems to be responsible for nitrous oxide (N2O) production by nitrifiers. The most prevalent denitrifiers are species of Pseudomonas, especially P. fluorescens, and Alcaligenes. This chapter presents a method for enumerating heterotrophic denitrifiers, measuring denitrifying activity of soils, and measuring denitrifying enzyme content of soils. The denitrification rate can be expressed as amount of N2O formed per gram of soil per time, which reflects enzyme concentration. Various modifications of the acetylene inhibition method to measure denitrification rates are being tested in a number of laboratories. The use of antibiotic-resistant denitrifier strains has been successfully used to examine denitrifier competitiveness under aerobic and anaerobic conditions.