Читать книгу Snyder and Champness Molecular Genetics of Bacteria - Tina M. Henkin - Страница 27

Probably the greatest advantage of bacterial genetics is the opportunity to do selections, by which very rare mutants and other types of strains can be isolated. To select a rare strain, billions of the bacteria are plated under conditions in which only the desired strain, not the bulk of the bacteria, can grow. In general, these conditions are called the selective conditions. For example, a nutrient may be required by most of the bacteria but not by the strain being selected. Agar plates lacking the nutrient then present selective conditions for the strain, since only the strain being selected multiplies to form a colony in the absence of the nutrient. In another example, the desired strain may be able to multiply at a temperature that would kill most of the bacteria. Incubating agar plates at that temperature would provide the selective condition. After the strain has been selected, a colony of the strain can be picked and the colony purified away from other contaminating bacteria under the same selective conditions.

The power of selection with bacterial populations is awesome. Using a properly designed selection, a single bacterium can be selected from among bill ions placed on an agar plate. If we could apply such selections to humans, we could find one of the few individuals in the entire human population of Earth with a particular trait.