Final answer:
Thioglycolate broth is a reducing medium used in microbiology to create varying oxygen environments to test bacteria's oxygen requirements.
Step-by-step explanation:
Thioglycolate broth is a reducing medium used in microbiology. It contains thioglycolate, a substance with strong reducing properties. The purpose of thioglycolate broth is to create varying oxygen environments in order to observe the oxygen requirements of bacteria. The oxygen slowly diffuses from the tube opening down the length of the tube, creating different oxygen levels throughout.