History of staining: Gram staining was introduced by which scientist?

Introduction / Context:
Gram staining is a cornerstone technique in bacteriology. It differentiates bacteria into Gram positive and Gram negative based on cell wall properties that affect dye retention. Knowing who developed the method helps connect methods to the history of microbiology.

Given Data / Assumptions:

• We need the name of the scientist who first introduced the Gram stain method in the late 19th century.
• Distractors include prominent microbiologists with other contributions.

Concept / Approach:
Hans Christian Gram, a Danish bacteriologist, introduced the Gram staining technique in 1884. It uses crystal violet and iodine to form a complex, followed by alcohol decolorization and safranin counterstain to distinguish cell wall types.

Step-by-Step Solution:

Verification / Alternative check:
Any microbiology textbook timeline places the Gram stain invention in 1884 by H. C. Gram with related lab protocol steps.

Why Other Options Are Wrong:

• B: Alfred Gram is not associated with the staining method.
• C: Robert Koch is a key figure in germ theory, but this misspelled variant does not match the stain inventor.
• D: Louis Pasteur pioneered vaccination and pasteurization, not the Gram stain.

Common Pitfalls:
Confusing Gram with other microbiology pioneers or accepting misspelled names.

Final Answer:
Christian Gram