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enrichment culture[in′rich·mənt ‚kəl·chər]
a culture containing microorganism cells grown on a selective nutrient medium. Enrichment cultures were proposed by the Russian microbiologist S. N. Vinogradskii. The special composition of the nutrient media creates conditions that promote the growth of microorganisms with certain physiological properties. For example, when soil, water, or sediment from a body of water is cultured on a medium containing glucose and several mineral salts but no nitrogen compounds, nitrogen-fixing microorganisms begin to grow in the culture. Enrichment cultures of bacteria that decompose cellulose can be obtained on a medium containing cellulose as the sole source of carbon.
Enrichment cultures must always be prepared before pure cultures of the microorganisms can be isolated. They can be obtained in the presence of growth factors, such as vitamins and amino acids, by adding a smaller number of bacterial cells to the medium. As a result, four to ten times more microorganisms can be found in soil and water than when they are cultured on media lacking growth factors.
A. A. IMSHENETSKII