Final answer:
The microorganism used to prove the germ theory was Bacillus anthracis, identified by Robert Koch, which is a spore-forming bacterium.
Step-by-step explanation:
The microorganism that was first used to prove the germ theory was Bacillus anthracis, identified by Robert Koch. As a spore-forming bacterium, it served as a crucial piece of evidence for the theory that diseases could be spread by microbes. Louis Pasteur and Robert Koch were instrumental figures during the Golden Age of Microbiology, contributing significantly to the development of this theory by demonstrating the role of microbes in disease and fermentation.
The microorganism that was first used to prove the germ theory was a spore former called Bacillus anthracis. This microorganism, which causes anthrax, was discovered by the German physician Robert Koch in the late 19th century.