Final answer:
Robert Koch was a major contributor to the germ theory of disease. He established Koch's postulates, which helped identify the causative microbes of specific diseases.
Step-by-step explanation:
One of the major contributors to the germ theory of disease was Robert Koch. He established a protocol known as Koch's postulates, which were used to definitively identify the causative pathogens of specific diseases. Koch's postulates stated that the cause of a specific disease could be attributed to a specific microbe. Through his work, Koch played a crucial role in the acceptance of the germ theory of disease.