Two people are commonly cited as early foundational figures in germ theory and the understanding that certain microscopic organisms cause disease, with Louis Pasteur and Robert Koch being central in the 19th century. Direct answer
- Louis Pasteur is widely credited with establishing the germ theory of disease and advancing microbiology in the 19th century. His experiments showed that microorganisms are responsible for fermentation and that disease-causing agents can be specific microorganisms, supporting the idea that microbes cause illness. Pasteur’s work also led to practices like pasteurization and influenced vaccination strategies.
- Robert Koch independently contributed key evidence linking particular microbes to specific diseases, formalizing methods to isolate and identify pathogens (Koch’s postulates). His work complemented Pasteur’s germ theory and helped solidify the causal relationship between germs and disease.
If you’d like, I can pull brief, citable summaries from reliable sources and note key dates and experiments.
