History of medical microbiology — discoverer of the cholera bacterium Which scientist is credited with identifying Vibrio cholerae as the causative agent of cholera during the late 19th century?

Introduction / Context:
Attribution of pathogen discovery is a foundational topic in medical microbiology. Cholera, a severe waterborne disease, was linked to its curved Gram-negative causative agent in the era when germ theory was being established. Knowing who identified Vibrio cholerae reinforces timelines and methods used to prove causation.

Given Data / Assumptions:

• The organism causing cholera is Vibrio cholerae.
• The period in question is the late 1800s, when Koch's postulates were being developed and applied.
• Multiple contemporary scientists made related contributions to germ theory.

Concept / Approach:
Robert Koch, renowned for pioneering bacteriology techniques and Koch's postulates, isolated and described numerous pathogens. He identified V. cholerae during investigations in Egypt and India. Pasteur contributed to vaccination and fermentation science; Virchow focused on cellular pathology; Lister advanced antiseptic surgery; Berthelot was a chemist, not a bacteriologist.

Step-by-Step Solution:
Recall the agent: Vibrio cholerae.Match the pathogen to the scientist known for isolation and etiological proof: Robert Koch.Eliminate other eminent figures whose primary work did not include cholera's bacterial discovery.

Verification / Alternative check:
Historical accounts detail Koch’s 1883–1884 expeditions and microscopic identification of the comma-shaped bacillus in cholera patients, fulfilling causation principles.

Why Other Options Are Wrong:

• A: Berthelot’s work centered on chemistry, not pathogen discovery.
• C: Pasteur did not discover the cholera bacterium.
• D: Virchow proposed cellular pathology; he did not isolate V. cholerae.
• E: Lister introduced antisepsis, unrelated to cholera’s discovery.

Common Pitfalls:
Confusing Koch’s identification of V. cholerae with John Snow’s epidemiological work on cholera transmission in London; Snow did not discover the bacterium.

Final Answer:
Robert Koch