Petri, Richard Julius (1852-1921)

German physician and bacteriologist

Richard Julius Petri's prominence in the microbiology community is due primarily to his invention of the growth container that bears his name. The Petri dish has allowed the growth of bacteria on solid surfaces under sterile conditions.

Petri was born in the German city of Barmen. Following his elementary and high school education he embarked on training as a physician. He was enrolled at the Kaiser Wilhelm-Akademie for military physicians from 1871 to 1875. He then undertook doctoral training as a subordinate physician at the Berlin Charité. He received his doctorate in medicine in 1876.

From 1876 until 1882 Petri practiced as a military physician. Also, during this period, from 1877 to 1879, he was assigned to a research facility called the Kaiserliches Gesundheitsamt. There, he served as the laboratory assistant to Robert Koch . It was in Koch's laboratory that Petri acquired his interest in bacteriology. During his stay in Koch's laboratory, under Koch's direction, Petri devised the shallow, cylindrical, covered culture dish now known as the Petri dish or Petri plate.

Prior to this invention, bacteria were cultured in liquid broth. But Koch foresaw the benefits of a solid slab of medium as a means of obtaining isolated colonies on the surface. In an effort to devise a solid medium, Koch experimented with slabs of gelatin positioned on glass or inside bottles. Petri realized that Koch's idea could be realized by pouring molten agar into the bottom of a dish and then covering the agar with an easily removable lid.

While in Koch's laboratory, Petri also developed a technique for cloning (or producing exact copies) of bacterial strains on slants of agar formed in test tubes, followed by subculturing of the growth onto the Petri dish. This technique is still used to this day.

Petri's involvement in bacteriology continued after leaving Koch's laboratory. From 1882 until 1885 he ran the Göbersdorf sanatorium for tuberculosis patients. In 1886 he assumed the direction of the Museum of Hygiene in Berlin, and in 1889 he returned to the Kaiserliches Gesundheitsamt as a director.

In addition to his inventions and innovations, Petri published almost 150 papers on hygiene and bacteriology. Petri died in the German city of Zeitz.

See also Bacterial growth and division; Growth and growth media; Laboratory techniques in microbiology