Potential of denitrifiers for soil environmental protection

Various surveys indicate that denitrifying bacteria represent 10–15% of the bacterial population in soil, water and sediment. They occur in almost every type of environmental niche examined to date and are thus likely to be available in a great variety of threatened or polluted ecosystems. Although systems undergoing bioremediation depend largely on metabolically adaptable aerobic bacteria and fungi for recycling the majority of the nutrients and elements, anaerobic zones containing polluting materials are commonly encountered, or entire contaminated systems may be oxygen-poor or anoxic. Bacterial denitrification can supply the most effective type of biotransformation in these environments, especially if nitrate or other N-oxides are naturally available or added. Denitrifiers use a broad range of inorganic and organic compounds as sources of carbon and energy with an efficiency of phosphorylation which is 67–71% of that during electron transport to oxygen. Moreover, nitrate is more soluble and often less expensive than oxygen. In this minireview, the distribution of denitrifiers and their ability to remove toxic inorganic and organic pollutants from soil environment is evaluated.