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Louis Pasteur (1822-1895) was a French chemist and biologist that contributed to science by his contributions in the fields of vaccination, fermentation, and the process of pasteurization. He refuted the spontaneous generation theory, by demonstrating the impossibility of microorganism without contamination. Pasteur was a defender of the germ theory of disease, and developed the first versions of vaccines against cholera, rabies and anthrax.