French chemist Louis Pasteur (1822–1895) and German bacteriologist Robert Koch (1843–1910) are considered the founders of bacteriology. In 1864, Pasteur devised a way to slowly heat foods and beverages to a high enough temperature to kill most of the microorganisms responsible for spoilage and disease. This method would not ruin or curdle the food—and is a process we now call pasteurization.

In 1882—by demonstrating that tuberculosis was an infectious disease caused by a specific bacterial species of Bacillus—Robert Koch set the groundwork for public-health measures that would reduce the occurrence of many diseases. His laboratory procedures, methodologies for isolating microorganisms, and four postulates (see below) for determining agents of disease gave medical investigators valuable insights into the control of bacterial infections.