The Little Things: Fanny Hesse’s Contribution to Microbiology

By Cyanne Cueva

Image credit U.S. National Library of Medicine, Wikimedia Commons

Special to The Enterprise

Fanny Angelina Hesse was born the oldest of 10 children in New York on June 22, 1850. Her parents were wealthy Dutch merchants who had just immigrated to the U.S. a few years before her birth. Not much is known of her early life, but when she was 15 her parents sent her to a finishing school in Switzerland to learn French and home economics. When she was 22, Fanny met a physician named Walther Hesse who she would go on to marry. The Hesse’s eventually settled in Dresden, Germany, where Walther worked as a district physician. In 1880, the Hesses moved to Berlin so that Walther could join the laboratory of bacteriologist Robert Koch, who was trying to find the cause of tuberculosis. Fanny often created highly detailed scientific illustrations for Walther’s publications that demonstrated her understanding of microbiology. Her family has preserved many of these drawings and watercolors.

For decades, microbiologists and bacteriologists used foods such as potatoes, egg whites, and meat to grow their microorganisms. The primary issue with these media was that they were opaque. To solve this, researchers such as Robert Koch used gelatin to grow their bacteria. Although gelatin was clear, it did not hold well in warm temperatures and was often digested into a goop by the bacteria that grew on it. Fanny proposed that her husband use agar instead. She had first heard about agar from her childhood neighbor who had emigrated from Indonesia and often used it to stabilize her jellies and jams in the summer. Walther proposed it to Koch, and the agar proved to be perfect due to its ability to stay solid in warm weather, resistance to the microbial enzymes that turned gelatin into goop, sterilizability, and long storage life. With this new medium for growing bacteria, Koch was able to release a paper on the Mycobacterium tuberculosis, where he mentioned the switch to agar, but neglected to credit either of the Hesses for the recommendation. Neither of the Hesses spoke much about their contributions with agar as they saw it as improper.

Thankfully, in 1939, two medical historians, Arthur Hitchens and Morris Leikind, wrote an article about agar as a growth medium and credited Fanny for her contribution. They even went so far as to hope it could be named “Mrs. Hesse’s medium.” Fanny Hesse’s contribution was pivotal to the field of microbiology. Agar remains the top growth medium for culturing microbes and has allowed for innumerable discoveries and innovations in health and other related fields.

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