The postulates to identify causative microorganisms are attributed to which scientist?

• A. Louis Pasteur
• B. Robert Koch
• C. Edward Jenner
• D. Carolus Linnaeus

Answer: (B)

This question hinges on who formalized a systematic method to prove causation between a microbe and a disease. Robert Koch developed a set of criteria, now known as Koch's postulates, that shaped microbiology by turning observation into experimental proof. The postulates require that the microbe be found in every case of the disease and not in healthy individuals, that it can be isolated in pure culture, that introducing it into a healthy host reproduces the disease, and that the same microbe can be re-isolated from the newly diseased host. These steps anchored the idea that specific organisms cause specific diseases and helped legitimize germ theory in a practical way. While contemporaries contributed to related ideas—Pasteur advanced germ theory and Jenner pioneered vaccination, Linnaeus organized classification—only Koch formalized this explicit investigative framework.