What are reducing media in microbiology?

Reducing media are used for growing anaerobic bacteria in the laboratory. Since obligate anaerobes do not grow in the presence of oxygen, this type of media uses a chemical substance, such as thioglycolate, to remove molecular oxygen that is dissolved in the media.

An example of a reducing medium is thioglycolate broth. This is also a differential medium because it allows the growth of other bacteria that are not strictly obligate anaerobes in different parts of the medium. For example, obligate aerobes grow at the top of the medium, where oxygen is present, while obligate anaerobes grow at the bottom of the test tube, where there is little to no oxygen.