Howard Fischer
Uppsala, Sweden

“Her contribution to bacteriology makes her immortal.”¹
—Medical historians Arthur Hitchens and Morris Leikind

“C’est un grand progrès!”²
—Louis Pasteur

Fanny Hesse (neé Angelina Fanny Eilshemius, 1850–1935) was born in New York City, the oldest of ten children in a family of Dutch origin. In 1874 she married German physician Walther Hesse (1846–1911) and moved with him to a mining community near Dresden. His patients were mostly uranium miners who had a high incidence of lung cancer. The dangers of radiation were unknown at the time, and the lung cancer was attributed to the miners’ occupational exposure to arsenic. Hesse wondered if inhaled microorganisms also contributed to their lung disease.

Because of this, he became interested in the emerging field of bacteriology. Fanny became his laboratory assistant and was a competent early medical technologist. She also was a medical illustrator and produced paintings of bacterial cultures. Fanny was the granddaughter of Swiss painter Louis Léopold Robert, and she had some of the family’s artistic ability. The Hesses worked in Dr. Robert Koch’s laboratory.³

Before 1882 or 1883, bacterial cultures were grown on coagulated egg white, meat, polenta, or potato slices.⁴ Koch had grown and identified the agent responsible for anthrax (Bacillus anthracis) on potato slices.⁵ Organisms were also cultured on gelatin, which was translucent and clearly showed the bacterial colonies, but melted in the laboratory on hot days or when cultures were incubated at high temperatures. In addition, some microbes liquefied the gelatin, producing an uninterpretable mess.

Fanny Hesse suggested trying agar as a culture medium. Agar, derived from Japanese seaweed (Gelidium corneum) contained, among other substances, a complex sugar. It gelled and remained solid at temperatures as high as 90° C, was transparent, and resisted the action of bacterial enzymes. She had learned about agar from a neighbor who had spent time in the Dutch colony of Indonesia, where agar-agar (“jelly” in the Malay language) had been used as a gelling agent for centuries. Fanny had used it to make fruit jellies.^6,7

After agar was mixed with other nutrients that supported bacterial growth, it turned out to be a valuable culture medium. It was this culture medium that finally enabled Koch to isolate Mycobacterium tuberculosis. Neither Koch nor anyone else gave credit to Fanny Hesse for this critical improvement in the way bacteria were cultured. She was never rewarded financially, either.⁸

In 2023, the bacterium Corynebacterium hesseae was named in honor of Angelina Fanny Hesse.⁹

References

1. Arthur Hitchens and Morris Leikind. “The introduction of agar-agar into bacteriology.” J Bacteriol, 35(7), 1939.
2. Andy Connelly. “Fanny Hesse.” Technicianjourney, June 20, 2019.
3. “Fanny Hesse.” Wikipedia.
4. Jennifer Tsang. “Fanny Hesse, the woman who introduced agar to microbiology.” The Microbial Menagerie, May 31, 2008.
5. Jay Hardy. “AGAR [sic] and the quest to isolate pure cultures.” Uploaded by mmc.gov.bd, Yumpu. https://www.yumpu.com/en/document/read/10170289/fanny-hesse-and-the-discovery-of-agar-in-microbiology-kochs-
6. “Fanny Hesse.” Wikipedia.
7. Corrado Nai. “Meet the forgotten woman who revolutionized microbiology with a simple kitchen staple.” Smithsonian, June 25, 2024.
8. “Fanny Hesse.” Wikipedia.
9. Elisabete Cappelli et al. “Expanding the bacterial diversity of the female urinary microbiome: description of eight new Corynebacterium species.” Microorganisms, 11(2), 2023.