Koch’s postulates, a cornerstone of medical microbiology, were established by Robert Koch during his research on anthrax caused by Bacillus anthracis. This framework proves microbial causation of diseases. The correct answer to the query is (B) Bacillus anthracis.​

Historical Context

Robert Koch developed his famous postulates in 1884 while investigating anthrax, a deadly livestock disease that also affects humans. He isolated Bacillus anthracis from infected animals, grew it in pure culture, and fulfilled all four criteria: presence in diseased hosts, isolation, disease reproduction in healthy hosts, and re-isolation. These steps shifted microbiology from theory to evidence-based science.​

Correct Answer Explanation

Koch first applied the postulates systematically to Bacillus anthracis, the anthrax bacterium, in cattle and other animals. Pure cultures inoculated into healthy subjects reproduced the disease, confirming causation. This work predates his tuberculosis research, marking anthrax as the key disease.​

Option Analysis

• (A) Mycobacterium tuberculosis: Koch identified this in 1882 and linked it to tuberculosis using modified postulates, earning the 1905 Nobel Prize. It came after anthrax work.​

• (B) Bacillus anthracis: Correct; Koch’s 1876-1884 anthrax studies birthed the postulates through isolation and animal experiments.​

• (C) Streptococcus pneumoniae: Causes pneumonia; identified later by Pasteur and others, not Koch’s postulate origin.​

• (D) Bacillus subtilis: Soil bacterium, non-pathogenic; unrelated to Koch’s disease causation research.​