Walther and Fanny Hesse

In 1881, Walther and Fanny Hesse made their most famous contribution to microbiology – one that owed as much to Fanny’s skill with jams and jellies as Walther’s expertise with bacteria. Walther Hesse (1846-1911) was a talented physician and scientist originally from Zittau, Germany. After graduating from the University of Leipzig, Walther began his career as a country doctor. Fanny Angelina Eilshemius (1850-1934) was the daughter of a wealthy New York merchant. The couple met when Walther traveled to New York as a ship’s doctor, and Fanny later toured Europe with her family. In 1874, they married and Walther settled down to his professional work. Fanny raised and educated their three sons, attended to her housework, helped Walther in the laboratory and illustrated his scientific papers.

After more than 10 years as a physician, Walther decided to study the bacteria that might be at the root of his patients’ illnesses. In 1881, he joined Robert Koch’s laboratory. One of Walther’s first projects was to isolate bacteria from the air. But, like most of his colleagues, Walther had a terrible time getting pure cultures. His options were few. He could boil a potato, cut slices with a sterilized knife and inoculate the slices with bacteria. However, a potato has only a limited number of nutrients and many bacteria simply refused to grow. Another possibility was a beef broth solidified with gelatin. Bacteria grew well on this medium, but it had a maddening tendency to turn into a cloudy liquid overnight. Many bacteria made enzymes that broke down the gelatin as they grew. Even when this wasn’t the case, the gelatin often liquefied if the laboratory became warm.

Walther confided his frustrations to Fanny. She thought she might have a solution. When she was growing up in New York, Fanny had a neighbor who had lived for a time in Java. The neighbor taught the Eilshemius family about agar-agar, a seaweed extract used in Asia to solidify jellies and thicken soups. Fanny had been successfully using agar-agar in her jams for years. Perhaps, she said, it would do the trick.

Walther discovered that agar-agar was indeed an ideal agent to gel the beef broth. At 100 C, it could be melted, mixed with the liquid broth and poured into dishes. The new medium was solid at room temperature and well above. Bacteria grew well on it but they could not break it down. Agar-agar was even translucent, a property that made identifying bacterial colonies and their characteristics much easier. Walther went on to make many contributions to microbiology: he helped develop new techniques to count bacteria in water samples, worked on the diagnosis of tuberculosis and helped introduce pasteurization to Germany. Fanny contributed detailed and highly accurate scientific illustrations. But Walther and Fanny’s breakthrough with agar-agar was what brought them lasting fame. Though it’s simply called agar now, the substance used in microbiology labs is the same one that originated in Fanny Hesse’s kitchen.


Hesse, Wolfgang. Walther and Angelina Hesse – early contributors to bacteriology. ASM News [serial online]. 1992;58:425-428. Available at: http://www.asmusa.org/mbrsrc/archive/SIGNIFICANT.htm Accessed September 22, 2000.