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Unformatted text preview: CHEMICALLY DEFINED MEDIA Chemically defined mediumone whose exact chemical composition is known. This means that every substance present, no matter how small the amount, is known, and also that exactly how much of every substance present is known. Media of this type are not used for general lab work. Since these media must be exceptionally pure, they are difficult and expensive to prepare, so they are only used when special work requires them. If the organism is a chemoheterotroph, the medium must contain organic growth factors that serve as a source of carbon and energy. Escherichia coli , is a good example of a chemoheterotroph with very simple requirements. Glucose is the only organic growth factor needed. With it plus some electrolytes and water, E. coli can synthesize everything else it needs . TABLE 6.2 P. 164 The other extreme is microbes that are described as fastidious. These require many organic The other extreme is microbes that are described as fastidious....
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