[2][3] With a grant from the Rockefeller Foundation she went to the laboratory of Monod at the Institut Pasteur, where she remained for the rest of her career.
Ullmann initially dealt with the effects of antibiotics at the Institut Pasteur and was able to elucidate, among other things, the mode of action of streptomycin (as an inhibitor of protein synthesis in bacteria).
Ullmann subsequently dealt with the mode of action of the whooping cough pathogen and its toxin.
She showed that the toxin increases the cAMP production in the host cell and thus disturbs their metabolism.
EAM President Philippe Sansonetti recalled all her contributions to microbiology in the "I n memoriam Agnes Ullmann" [6] In 1978, with André Lwoff, she published a collection of essays by Jacques Monod[7] and she published two anthologies in memory of him.