Marie worked as a secretary and science writer to her spouse and served as his amanuensis.

The students and colleagues of Louis Pasteur acknowledged the importance she had for him in his work as his assistant.

She grew the silkworms he needed for his experiment with their diseases, and she took care of the children he tried his famous experimental treatment on.

It seems that for years afterward, famous crystallographer, physicist and mathematician Jean Baptiste Biot, Madame Marie Pasteur and Louis' father, Jean Joseph cooperated in providing Louis with moral support.

For instance, in a letter by Biot to Louis father: "your son is ours also and we share with Marie all our love for him, too".