How did Louis Pasteur and Robert Koch contribute to the development of germ theory?

Louis Pasteur and Robert Koch were pivotal in establishing germ theory, the principle that specific microorganisms cause infectious diseases.12

Louis Pasteur provided foundational evidence by proving that fermentation and the souring of milk are caused by living microorganisms, effectively disproving the theory of spontaneous generation. He further advanced the field by developing vaccines for diseases such as anthrax and rabies.12

Robert Koch complemented this work by developing rigorous laboratory methods to isolate, cultivate, and examine bacteria. He invented techniques like the hanging-drop culture and staining methods to identify specific pathogens. Most significantly, he formulated Koch’s postulates, a set of four criteria used to scientifically prove that a specific microorganism is the causative agent of a particular disease. Using these methods, he successfully identified the bacteria responsible for tuberculosis and cholera. Together, their work transformed pathology and medicine by shifting the focus toward identifying and targeting specific microbial causes of illness.134