Electron transport system activity in soil, sediment, and pure cultures

The major purpose of this review is to examine recent developments in the measurement of electron transport system (ETS) activity (also known as dehydrogenase activity) in soil, sediment, and pure cultures. Since enzyme assays, (such as ETS) measurements can measure the general bioactivity of a large part of the microbial community in soil or sediment, various attempts have been made to develop rapid, simple, and reliable assays for such activities, particularly ETS activity. Since ETS activity is a consequence of many metabolic processes, the ability to measure this activity would be useful in assessing the status of various soils and sediments. Tetrazolium salts, like 2,3,5-triphenyltetrazolium chloride (TTC) and 2-(p-iodophenyl)-3-(p-nitrophenyl)-5- phenyltetrazolium chloride (INT), can be biologically reduced to their respective tetrazolium formazan by soil and sediment microorganisms and enzymes. The formazan produced can then be used as a measure of ETS activity in soil and sediment. The chemical, physical, and biological factors that influence ETS activity and their relationship to respiration will be surveyed.