Google the word microbiology, and the first few images you’ll see are Petri dishes containing solid growth media, also known as agar plates. Microbiologists use these plates containing food to grow the microorganisms they study.
A key ingredient in solid growth media is called agar. It is the solidifying agent. This ingredient originated from a relatively unknown person — her name does not come to mind as quickly as Leeuwenhoek or Pasteur — though her contribution was arguably one of the most important to the field’s progress.
This article introduces you to Angelina Fanny Hesse, the woman who made this significant contribution to microbiology, and describes the imporance of this ingredient in microbiological growth media that scientists around the world use daily.
What is agar?
Agar is the solidifying agent in solid microbiological growth media, meaning it makes it possible to grow microorganisms on a solid agar plate surface instead of in liquid broth. In liquid, microbes are in suspension, and on agar plates, microbes can grow as individual colonies. It is crucial to separate individual colonies to examine single species of microbes. In liquid, however, it is challenging to separate multiple species.
Before agar, solid microbiological growth media looked like potato slices, gelatin, polenta, meat, and coagulated egg whites. The closest ingredient to agar was gelatin. But gelatin presented problems for microbiologists: it melts at a temperature commonly used to grow microorganisms, 37ºC (98.6ºF), which is human body temperature. Some bacteria can even degrade it.
Finding liquid instead of solid media when you return to your agar plates would have been understandably frustrating because the individual colonies you had hoped for are now back into suspension.
Without a suitable solid medium, microbiologists needed to find something better.
How did we come to use agar in microbiology?
Angelina Fanny Hesse, called Lina by her family, knew about something better for making solid growth media. But who was she? Lina was married to a man named Walther Hesse, who, while working in the famous microbiologist Robert Koch’s lab, was struggling to grow microorganisms from air using gelatin.
When Walther noticed Lina’s jellies and puddings were not melting, he asked about it, and she shared her secret cooking ingredient: agar. Lina’s experience with agar came from her background. Born to a Swiss mother and a Dutch father, she grew up in New York, where she learned about agar from a Dutch neighbor who had lived in Indonesia (a Dutch colony at the time). This versatile substance, common in Indonesian desserts, had remarkable properties — it remained solid even in warm weather.
Walther then took the helpful information about agar he had learned from Lina and shared it with Koch. They finally had a substance similar to gelatin that didn’t melt at 37ºC, and bacteria couldn’t degrade it either. Agar became the primary solidifying agent in their solid growth media, and Koch wrote about it to share this with the scientific community. One thing he left out was who made this contribution. He gave credit to neither Lina nor Walther. So, Lina Hesse remains relatively unknown even today.
Angelina Fanny Hesse, the scientific illustrator
Lina Hesse not only contributed agar to microbiology, but she also worked in Koch’s lab with Walther as an assistant, much like one of today’s lab technicians, and as a scientific illustrator. Walther used her drawings of his microscopy in his publications. In an article written by Lina’s grandson, Wolfgang Hesse, he describes her illustrations of intestinal bacteria for Walther’s 1908 publication that she drew as “magnified colonies on agar plates during different growth phases and colored them with watercolors in a highly accurate way, indicating her thorough understanding of bacteriology and microscopy.”
Angelina Fanny Hesse, a name to recognize
Angelina Fanny Hesse’s contribution of agar to microbiology is arguably one of the most important in moving the field forward. Almost every microbiologist today uses this media ingredient; however, the woman who shared it has only recently started to become more well-known. I hope this article will help bring more recognition to the name Angelina Fanny Hesse.
Further Reading
This post contains affiliate links — see my disclosure policy.
- Discovering the Microbial World: Create Your Own Agar Plates
- 5 Ways to Share the Microbial World With Your Children
- Elizabeth Bugie Gregory: A Forgotten Figure in Streptomycin Discovery
- More on Angelina Fanny Hesse: Smithsonian Magazine article
- Kickstarter for a graphic novel about Fanny Angelina Hesse
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