Nitrifying bacteria
Small group of oxygen-requiring bacteria that use nitrogen as an energy source.
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| Nitrifying bacteria |
These microorganisms are important in the nitrogen cycle as converters of soil ammonia to nitrates, compounds usable by plants. The nitrification process requires two distinct groups: bacteria that convert ammonia to nitrites, and bacteria that convert nitrites to nitrates. In agriculture, irrigation with dilute solutions of ammonia results in an increase in soil nitrates through the action of nitrifying bacteria. See also denitrifying bacteria.
Denitrifying Bacteria
Soil microorganisms whose action results in the conversion of nitrates in soil to free atmospheric nitrogen, thus exhausting soil fertility and reducing agricultural productivity.
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| Denitrifying Bacteria |
Without denitrification, earth's nitrogen supply would eventually accumulate in the oceans, since nitrates are highly soluble and are continuously leached from the soil into nearby bodies of water. See also nitrifying bacteria.
Coliform Bacteria
Rod-shaped bacteria usually found in the intestinal tracts of animals, including humans.
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| Coliform Bacteria |
Coliform bacteria do not require but can use oxygen, and they do not form spores. They produce acid and gas from the fermentation of lactose sugar. Their presence in the water supply indicates recent contamination by human or animal feces. Chlorination is the most common preventive water treatment
Sheathed Bacteria
Group of bacteria found widely in nature in slow-running water.
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| Sheathed Bacteria |
Many species are attached to underwater surfaces. They are characterized by a threadlike, branching arrangement of cells enclosed in a sheath. The sheaths of some are variously encrusted with iron or manganese oxides, depending on the water. One of the best-known is a common species, Sphaerotilus natans; in polluted water it has thin, colourless sheaths, and in unpolluted water containing iron it has yellow-brown, iron-encrusted sheaths that often grow into long slimy tassels.
Sulfer Bacteria
Any of a diverse group of bacteria that are capable of metabolizing sulfur and its compounds and are important in the sulfur cycle.
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| sulfer Bacteria |
Members of the genus Thiobacillus, widespread in marine and terrestrial habitats, react with sulfur to produce sulfates useful to plants; in deep ground deposits they generate sulfuric acid, which dissolves metals in mines and corrodes concrete and steel. Desulfovibrio desulficans reduces sulfates in waterlogged soils and sewage to hydrogen sulfide, a gas with the common rotten-egg odour.
Budding Bacteria
Group of bacteria that reproduce by budding.
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| Budding Bacteria |
Each bacterium divides following unequal cell growth; the mother cell is retained, and a new daughter cell forms. In budding, the cell wall grows from one point on the cell rather than throughout the cell; this type of growth permits the development of more complex structures and processes. Most budding bacteria are aquatic and can attach to surfaces by their stalks; some are free-floating.
Source: Britannica encyclcopedia
