What did Robert Koch publish in 1877?

• A. Discovered Vibrio cholerae and determined its routes of transmission
• B. Awarded Nobel Prize
• C. Published methods for fixing bacteria on slides and staining for identification and comparison
• D. Developed method for obtaining pure cultures

Answer: (C)

In 1877 the key contribution is his published methods for fixing bacteria on slides and staining them to reveal their appearance under the microscope. Fixation locks the cells in place and preserves their structure, while staining provides contrast so you can see shape, size, and arrangement (such as rods or cocci). With these techniques, bacteria become observable and distinguishable, enabling identification and comparison across species and laying the groundwork for modern bacteriology. The other events listed happened later: understanding cholera's agent and transmission occurred in the 1880s, Koch’s Nobel Prize came in 1905, and methods for obtaining pure cultures became prominent after this period.