Bacteriology is a branch of biology that studies the morphology, ecology, genetics and biochemistry of bacteria, as well as many other aspects related to them. The identification, classification and characterization of bacterial species is a subdivision of microbiology. This is the study of bacteria and their relation to medicine. Identifying and characterizing bacteria associated with diseases led to advances in pathogenic bacteriology. This has led to many successful advances like effective vaccines, such as diphtheria and tetanus. Bacteriology has also provided the discovery of antibiotics. The connection of microorganisms to disease can be dated back to the nineteenth century when Robert Koch introduced the science of microorganisms to the medical field. He identified that bacteria was the cause of infectious diseases and the process of fermentation in diseases. Louis Pasteur developed techniques to produce vaccines. Both Koch and Pasteur were instrumental in improving antisepsis in medical treatment. The importance of bacteria was recognized as it led to the study of disease prevention and treatment of diseases by vaccines.