This is generally done by introducing nutrients or environmental conditions that only allow the growth of an organism of interest.
Enrichment cultures are used to increase a small number of desired organisms to detectable levels.
[2] The microbiologist (and botanist) Martinus Beijerinck is credited with developing the first enrichment cultures.
[4] Media with a high salt concentration will select for halophiles.
Selenite broth is used to selectively isolate Salmonella species.