As a leading microbiologist during the 1800s, the theory completed several studies leading to the germ theory of disease.

Pasteur disproved the theory of abiogenesis

Explanation:

Louis Pasteur was the scientist who disproved the theory of spontaneous generation. Pasteur disproved the theory of abiogenesis by using swan-necked flask. He used two swan-necked flask in which media was present and he heated the media to sterile it.

Then he broke the neck of one flask and observed that after some time the broth in broken neck flask showed growth but the unbroken necked flask remained sterile.

So he concluded that flask with swan-necked do not allowed microbe and air passed to the media while air can easily pass to media in broken neck flask which allowed microbe to grow.  

He also gave germ theory of disease which says that disease is caused by microorganisms.