Explanation

Louis Pasteur (1822–1895) was a pioneering microbiologist and chemist whose work bridged both fields:

As a Chemist:

• Discovered molecular chirality (optical isomers).
• Studied fermentation, proving it was caused by microorganisms.

As a Microbiologist:

• Developed pasteurization (heat treatment to kill microbes in food).
• Created vaccines for rabies and anthrax.
• Disproved spontaneous generation (germ theory of disease).