Robert Koch was a German physician and scientist who is considered one of the founders of bacteriology. He developed experimental techniques to isolate bacteria and prove they cause specific diseases, such as showing that Bacillus anthracis causes anthrax. Koch established four steps, known as Koch's postulates, to identify the microorganisms that cause diseases. His work helped prove the germ theory of disease and led to advances in combating disease through isolation of pathogens like anthrax, tuberculosis, and cholera.