**Core Concept**
The discovery of Mycobacterium tuberculosis is a significant milestone in the field of microbiology, marking the identification of a major human pathogen responsible for tuberculosis (TB) disease. This bacterium's discovery led to a better understanding of its transmission, pathogenesis, and the development of diagnostic tools and treatments for TB.

**Why the Correct Answer is Right**
Mycobacterium tuberculosis was discovered by Robert Koch, a German physician and microbiologist, in 1882. Koch's work on the bacterium was groundbreaking, and he developed the "gold standard" for establishing a causal relationship between a microorganism and a disease, known as Koch's postulates. He isolated the bacterium from human tissue and demonstrated its ability to cause disease in animals, thereby establishing its role in TB. Koch's discovery revolutionized the field of microbiology and led to significant advances in the diagnosis and treatment of TB.

**Why Each Wrong Option is Incorrect**
**Option A:** Louis Pasteur made significant contributions to microbiology, including the development of vaccination and pasteurization, but he did not discover M. tuberculosis.
**Option C:** Joseph Lister was a British surgeon who made important contributions to antiseptic practices and the prevention of infection, but he was not involved in the discovery of M. tuberculosis.
**Option D:** Edward Jenner was an English physician who developed the first vaccine against smallpox, but he did not discover M. tuberculosis.

**Clinical Pearl / High-Yield Fact**
Koch's postulates remain a fundamental principle in microbiology, serving as a framework for establishing a causal relationship between a microorganism and a disease. This concept is still widely used today in the diagnosis and investigation of infectious diseases.

**✓ Correct Answer: B. Robe koch**