Title: Microorganism
Content:  modern science. The earliest known idea to indicate the possibility of diseases spreading by yet unseen organisms was that of the Roman scholar Marcus Terentius Varro in a first-century BC book entitled On Agriculture in which he called the unseen creatures animalcules, and warns against locating a homestead near a swamp: "… and because there are bred certain minute creatures that cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and they cause serious diseases." In The Canon of Medicine (1020), Avicenna suggested that tuberculosis and other diseases might be contagious.
Title: Germ theory of disease
Content:  invisible living bodies. In 1646, Kircher (or "Kirchner", as it is often spelled), wrote that "a number of things might be discovered in the blood of fever patients." When Rome was struck by the bubonic plague in 1656, Kircher investigated the blood of plague victims under the microscope. He noted the presence of "little worms" or "animalcules" in the blood and concluded that the disease was caused by microorganisms. He was the first to attribute infectious disease to a microscopic pathogen, inventing the germ theory of disease, which he outlined in his Scrutinium Physico-Medicum (Rome 1658). Kircher's conclusion that disease was caused by microorganisms was correct, although it 
Title: Testing cosmetics on animals
Content:  how their bodies worked. "Proving the germ theory of disease was the crowning achievement of the French scientist Louis Pasteur. He was not the first to propose that diseases were caused by microscopic organisms, but the view was controversial in the 19th century and opposed the accepted theory of 'spontaneous generation'". The idea of germs and other microscopic organisms was a completely new idea and wouldn't have come to be without the use of animals. In 1665, scientists Robert Hooke and Antoni van Leeuwenhoek discovered and studied how germs worked. They published a book about their discovery, which was not accepted by 
Title: Microorganism
Content:  disease.  In 1876, Robert Koch (1843–1910) established that microorganisms can cause disease. He found that the blood of cattle that were infected with anthrax always had large numbers of Bacillus anthracis. Koch found that he could transmit anthrax from one animal to another by taking a small sample of blood from the infected animal and injecting it into a healthy one, and this caused the healthy animal to become sick. He also found that he could grow the bacteria in a nutrient broth, then inject it into a healthy animal, and cause illness. Based on these experiments, he devised criteria for establishing a causal link between a microorganism and a disease and these are now known as Koch's postulates. Although these postulates 
Title: Epidemiology
Content:  In the middle of the 16th century, a doctor from Verona named Girolamo Fracastoro was the first to propose a theory that these very small, unseeable, particles that cause disease were alive. They were considered to be able to spread by air, multiply by themselves and to be destroyable by fire. In this way he refuted Galen's miasma theory (poison gas in sick people). In 1543 he wrote a book De contagione et contagiosis morbis, in which he was the first to promote personal and environmental hygiene to prevent disease. The development of a sufficiently powerful microscope by Antonie van Leeuwenhoek in 1675 provided 
Title: Microbiology
Content:  a homestead in the vicinity of swamps "because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and thereby cause serious diseases." Persian scientists hypothesized the existence of microorganisms, such as Avicenna in his book The Canon of Medicine, Ibn Zuhr (also known as Avenzoar) who discovered scabies mites, and Al-Razi who gave the earliest known description of smallpox in his book The Virtuous Life (al-Hawi). In 1546, Girolamo Fracastoro proposed that epidemic diseases were caused by transferable seedlike entities that could transmit infection 
Title: Germ theory of disease
Content:  The Italian Agostino Bassi was the first person to prove that a disease was caused by a microorganism when he conducted a series of experiments between 1808 and 1813, demonstrating that a "vegetable parasite" caused a disease in silkworms known as calcinaccio which was devastating the French silk industry at the time. The "vegetable parasite" is now known to be a fungus pathogenic to insects called Beauveria bassiana (named after Bassi).
Title: Microbiome
Content:  called animalcules, mainly from water, mud, and dental plaque samples, and discovered biofilms as a first indication of microorganisms interacting within complex communities. Robert Koch's explanation of the origin of human and animal diseases as a consequence of microbial infection and development of the concept of pathogenicity was an important milestone in microbiology. These findings shifted the focus of the research community and the public on the role of microorganisms as disease-forming agents that needed to be eliminated. However, comprehensive research over the past century has shown only a small proportion of microorganisms are associated with disease or pathogenicity. The overwhelming majority of microbes are essential for ecosystem functioning and known for beneficial interactions with other microbes 
Title: Bacteria
Content:  handwashing in his hospital in the 1840s predated the spread of the ideas about germs themselves and attributed diseases to "decomposing animal organic matter", Lister was active later. Robert Koch, a pioneer in medical microbiology, worked on cholera, anthrax and tuberculosis. In his research into tuberculosis Koch finally proved the germ theory, for which he received a Nobel Prize in 1905. In Koch's postulates, he set out criteria to test if an organism is the cause of a disease, and these postulates are still used today. Ferdinand Cohn is said to be a founder of bacteriology, studying bacteria from 1870. Cohn was the first to classify bacteria based on their morphology. Though it was known in the nineteenth century that bacteria are the cause 
Title: Bacteriology
Content:  The discovery of the connection of microorganisms to disease can be dated back to the nineteenth century, when German physician Robert Koch introduced the science of microorganisms to the medical field. He identified bacteria as the cause of infectious diseases and process of fermentation in diseases. French scientist Louis Pasteur developed techniques to produce vaccines. Both Koch and Pasteur played a role in improving antisepsis in medical treatment. This had an enormous positive effect on public health and gave a better understanding of the body and diseases. In 1870-1885 the modern methods of bacteriology technique were introduced by the use of stains and by the method of separating mixtures of organisms on plates of nutrient media. Between 1880 and 1881 Pasteur produced two successful vaccinations for animals against diseases caused by bacteria and it was successful. The importance of bacteria was recognized as it led to a study of disease prevention and treatment of diseases by vaccines. Bacteriology has developed and can be studied in agriculture, marine biology, water pollution, bacterial genetics and biotechnology.

Question: who established the idea that microorganisms play a role in disease?
Answer: Robert Koch.
Agostino Bassi.