The study of bacteria is the subject of a branch of microbiology called bacteriology. Bacteriology is further broken down into several sub-divisions that focus on bacteria in specific environments, such as marine and industrial bacteriology.
With the advent of the microscope, scientists began studying the organisms called bacteria. Between 1853 and 1872, Ferdinand Cohn classified the morphology of many bacteria. However, it was the work of scientists Robert Koch and Louis Pasteur that made the connection between bacteria and the processes of fermentation and disease. Development of drugs to combat diseases caused by bacteria led to the founding of the branch of medicine known as immunology.