Denitrifying bacteria
Encyclopedia
Denitrifying bacteria form a necessary part of the process known as denitrification
as part of the nitrogen cycle
, their primary purpose being to metabolise
nitrogenous compounds
, with the assistance of the nitrase reductase enzyme
, to turn oxide
s back to nitrogen gas or nitrous oxides for energy generation. This process takes place only in the absence of oxygen
, as most denitrifying bacteria are facultative aerobes (prefers to use oxygen as their terminal electron acceptors), however, they could also utilize nitrate instead. Therefore, denitrification can only be performed under anaerobic conditions. This is the main reason why denitrification mostly occurs in the deep substrata of the soil
, or in areas of stagnant water.
The process of denitrification lowers the fertility of the soil and thus is less common in areas where the land is rather well-cultivated
. But this loss of nitrogen to the atmosphere can eventually be regained via introduced food and water, as part of the nitrogen cycle. Some nitrogen may also be fixated
by species of nitrifying bacteria
and the cyanobacteria.
Denitrification
also becomes the key pathway for dissimilative nitrate reduction, which is the process in which nitrates are reduced from the soil, the former being highly toxic for living organisms. Unlike its antithesis, denitrification tends to produce large amounts of by-product
s.
The most common denitrification process is basically outlined below, with the nitrogen oxides being converted back to gaseous nitrogen (as opposed to that of nitrifying bacteria):
As can be seen, the result is one molecule of nitrogen (consisting of two atoms) and six molecules of water.
Denitrifying bacteria themselves include several species of pseudomonas
, alkaligenes and bacillus
. By their activity the losses of nitrogen into the atmosphere is roughly balanced by that which is released into the soil by nitrifying bacteria
, forming a relatively balanced cycle.
that reduce nitrates or nitrites to nitrogen-containing gases.
Potential examples includeThiobacillus denitrificans, Micrococcus
denitrificans, Paracoccus
denitrificans and Pseudomonas
. This is important as it allows nitrogen to be recycled (see nitrogen cycle
) back into the atmosphere
.
These bacteria have also been implicated in depletion of soil fertility, and thereby agricultural productivity that can help the source (the Sun) to give the best implantation it can give.
Denitrification
Denitrification is a microbially facilitated process of nitrate reduction that may ultimately produce molecular nitrogen through a series of intermediate gaseous nitrogen oxide products....
as part of the nitrogen cycle
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...
, their primary purpose being to metabolise
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
nitrogenous compounds
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
, with the assistance of the nitrase reductase enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
, to turn oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
s back to nitrogen gas or nitrous oxides for energy generation. This process takes place only in the absence of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, as most denitrifying bacteria are facultative aerobes (prefers to use oxygen as their terminal electron acceptors), however, they could also utilize nitrate instead. Therefore, denitrification can only be performed under anaerobic conditions. This is the main reason why denitrification mostly occurs in the deep substrata of the soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
, or in areas of stagnant water.
The process of denitrification lowers the fertility of the soil and thus is less common in areas where the land is rather well-cultivated
Tillage
Tillage is the agricultural preparation of the soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shovelling, picking, mattock work, hoeing, and raking...
. But this loss of nitrogen to the atmosphere can eventually be regained via introduced food and water, as part of the nitrogen cycle. Some nitrogen may also be fixated
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
by species of nitrifying bacteria
Nitrifying bacteria
Nitrifying bacteria are chemoautotrophic or chemolithotrophs depending on the genera bacteria that grow by consuming inorganic nitrogen compounds...
and the cyanobacteria.
Denitrification
Denitrification
Denitrification is a microbially facilitated process of nitrate reduction that may ultimately produce molecular nitrogen through a series of intermediate gaseous nitrogen oxide products....
also becomes the key pathway for dissimilative nitrate reduction, which is the process in which nitrates are reduced from the soil, the former being highly toxic for living organisms. Unlike its antithesis, denitrification tends to produce large amounts of by-product
By-product
A by-product is a secondary product derived from a manufacturing process or chemical reaction. It is not the primary product or service being produced.A by-product can be useful and marketable or it can be considered waste....
s.
The most common denitrification process is basically outlined below, with the nitrogen oxides being converted back to gaseous nitrogen (as opposed to that of nitrifying bacteria):
- 2 NO3- + 10 e- + 12 H+ → N2 + 6 H2O
As can be seen, the result is one molecule of nitrogen (consisting of two atoms) and six molecules of water.
Denitrifying bacteria themselves include several species of pseudomonas
Pseudomonas
Pseudomonas is a genus of gammaproteobacteria, belonging to the family Pseudomonadaceae containing 191 validly described species.Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the...
, alkaligenes and bacillus
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...
. By their activity the losses of nitrogen into the atmosphere is roughly balanced by that which is released into the soil by nitrifying bacteria
Nitrifying bacteria
Nitrifying bacteria are chemoautotrophic or chemolithotrophs depending on the genera bacteria that grow by consuming inorganic nitrogen compounds...
, forming a relatively balanced cycle.
Denitrifying bacteria
A group of bacteriaBacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
that reduce nitrates or nitrites to nitrogen-containing gases.
Potential examples includeThiobacillus denitrificans, Micrococcus
Micrococcus
Micrococcus is a genus of bacteria in the Micrococcaceae family. Micrococcus occurs in a wide range of environments, including water, dust, and soil. Micrococci have Gram-positive spherical cells ranging from about 0.5 to 3 micrometers in diameter and are typically appear in tetrads...
denitrificans, Paracoccus
Paracoccus
In taxonomy, Paracoccus is a genus of the Rhodobacteraceae.-External links:...
denitrificans and Pseudomonas
Pseudomonas
Pseudomonas is a genus of gammaproteobacteria, belonging to the family Pseudomonadaceae containing 191 validly described species.Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the...
. This is important as it allows nitrogen to be recycled (see nitrogen cycle
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...
) back into the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
.
These bacteria have also been implicated in depletion of soil fertility, and thereby agricultural productivity that can help the source (the Sun) to give the best implantation it can give.