Answer:
Koch's postulates are a set of criteria that are used to establish a causal relationship between a microbe and a specific disease. The four postulates are:
- The microbe must be present in every case of the disease.
- The microbe must be isolated from the host with the disease and grown in pure culture.
- The specific disease must be reproduced when the microbe is introduced into a healthy host.
- The microbe must be re-isolated from the host with the disease and shown to be the same as the original microbe.
These postulates were first proposed by the German physician and scientist Robert Koch in the late 19th century, and they remain an important tool in the field of medical microbiology.