Short answers, pulled from the story.
Robert Koch was a German physician and microbiologist who lived from the 11th of December 1843 to the 27th of May 1910. He discovered the causative agents of anthrax, tuberculosis, and cholera, and is regarded as one of the main founders of modern bacteriology.
Robert Koch won the 1905 Nobel Prize in Physiology or Medicine for his investigations and discoveries in relation to tuberculosis. He had reported Mycobacterium tuberculosis as the cause of the disease in 1882.
Koch's postulates are generalized principles used to determine whether a pathogen causes a specific disease. Although Koch worked out the underlying principles, the postulates were formulated by his assistant Friedrich Loeffler in 1883, with a fourth added by the American plant pathologist Erwin Frink Smith in 1905.
Koch announced tuberculin in 1890 as a tuberculosis treatment, but clinical trials were disastrous. Rudolf Virchow's autopsy report on 21 treated subjects, given on the 7th of January 1891, found that patients died because of the treatment, and the German official report later that year declared tuberculosis was not cured. Tuberculin is now used to test for hypersensitivity in tuberculosis patients.
Robert Koch identified the cholera bacterium, isolating it in pure culture on the 7th of January 1884 in Calcutta, India, and describing it as a little bent, like a comma. He traced the source of the infection to the river Ganges. The bacterium was renamed Vibrio cholera by his colleague Richard Friedrich Johannes Pfeiffer in 1896.
World Tuberculosis Day falls on the 24th of March because that is the day in 1882 when Robert Koch announced his discovery of the tuberculosis bacterium before the German Physiological Society in Berlin. The World Health Organization has observed the day every year since 1982.
Robert Koch began using agar to grow pure bacterial cultures in 1881, on a suggestion from his assistant Walther Hesse, who got the idea from his wife Fanny Hesse. His assistant Julius Richard Petri published a minor modification of Koch's plating method in 1887, and the resulting container became known as the Petri dish.