How did Robert Koch identify the bacteria that cause tuberculosis and cholera?

Robert Koch identified the causative agents of tuberculosis and cholera through meticulous laboratory techniques and field investigations.12

Tuberculosis

Koch discovered the tubercle bacillus in 1882 by modifying staining methods to visualize the organism in infected tissues. To confirm its role as the cause of tuberculosis, he successfully isolated the bacteria in pure culture using a succession of media and subsequently induced the disease in animals through inoculation.1

Cholera

Koch’s investigation into cholera began during an outbreak in Egypt, where he identified a comma-shaped bacterium (vibrio) he suspected was the cause. He later confirmed this hypothesis while working in India, where the disease was endemic. Through his research, he identified the organism and established that it was transmitted via contaminated drinking water, food, and clothing.1

These breakthroughs were part of Koch's broader contributions to bacteriology, where he pioneered methods for cultivating, isolating, and examining microorganisms in the laboratory.2