60] Purification of electron-transfer components of nitrifying and denitrifying bacteria and assay of intermediates

Abstract

This chapter describes the purification of electron-transfer components of nitrifying and denitrifying bacteria and assay of intermediates. Certain heterotrophic nitrifying microorganisms (e.g., Arthrobacter, Pseudomonas, and Aspergillus species) also generate nitrite and nitrate by the successive production and catabolism of nitroso and nitro organic compounds. The extensiveness of heterotrophic nitrification in nature, and the mechanisms by which it is carried out, are not yet known; but the autotrophic mode appears greatly to predominate. A number of ordinarily aerobic bacterial species can grow anaerobically at the expense of nitrate or nitrite respiration that yields dinitrogen as the end product. This type of nitrate reduction, called denitrification, is distinguished from: (1) assimilatory nitrate and nitrite reduction in green plants, algae, fungi, and certain bacteria that yield and and are regulated by the nutritional need for ammonia, and (2) dissimilatory reduction of nitrate to nitrite (that may accumulate unchanged, or may undergo reduction to ammonia in a variety of anaerobic bacteria—for example, E. coli and Veillonella alkalescens , respectively), which is controlled by availability or lack of oxygen. Aerobically grown cells produce little or none of the denitrifying enzymes, but simple anaerobic incubation derepresses their synthesis.