Any of a diverse group of bacteria that are capable of metabolizing sulfur and its compounds and are important in the sulfur cycle. 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.
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Small group of oxygen-requiring bacteria that use nitrogen as an energy source. 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. Seealso denitrifying bacteria.
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Soil microorganisms whose action results in the conversion of nitrates in soil to free atmospheric nitrogen, thus exhausting soil fertility and reducing agricultural productivity. 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. Seealso nitrifying bacteria.
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Rod-shaped bacteria usually found in the intestinal tracts of animals, including humans. 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.
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Group of microscopic, single-celled organisms that inhabit virtually all environments, including soil, water, organic matter, and the bodies of multicellular animals. Bacteria are distinguished in part by their morphological and genetic features; for instance, they may have spherical, rodlike, or spiral shapes. They also can be divided into two main groups, gram-positive or gram-negative, based on the structure of their cell wall and their reaction to the gram stain. Many bacteria swim by means of flagella (see flagellum). The DNA of most bacteria is found in a single circular chromosome and is distributed throughout the cytoplasm rather than contained within a membrane-enclosed nucleus. Though some bacteria can cause food poisoning and infectious diseases in humans, most are harmless and many are beneficial. They are used in various industrial processes, especially in the food industry (e.g., the production of yogurt, cheeses, and pickles). Bacteria are genetically distinct from the archaea. As prokaryotic organisms (having no membrane-bound nucleus), they are also distinct from eukaryotes. Seealso budding bacteria, coliform bacteria, cyanobacteria, denitrifying bacteria, nitrifying bacteria, sheathed bacteria, sulfur bacteria.
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Some strains are sensitive to ampicillin.