Google doodle of the day: Google celebrates Danish microbiologist Hans Christian Gram's 166th birthday

Today, Google is celebrating the 166th birthday of Hans Christian Gram with a doodle. The Danish microbiologist gained international recognition for his development of the Gram stain – a method of staining bacteria, to make them more noticeable under a microscope.

The art illustrates Gram's work from his experiments to a closer look of bacteria under the microscope. The beautiful art in the doodle was created by Mikkel Sommer, a Danish guest artist.

Hans Christian Gram was born on the 13th of September 1853 in Copenhagen. Gram joined the University of Copenhagen in 1878 and graduated in 1883, earning an MD. During his time at the university, Gram served as an assistant in botany to the zoologist Japetus Steenstrup. After his graduation, Gram travelled through Europe to study bacteriology and pharmacology.

During his travels, Gram noticed that treating a smear of bacteria with a cocktail of crystal violet stain, organic solvent, and iodine solution would reveal key differences in the structure and biochemical function of various samples. In 1884, Gram published his findings in a scholarly journal in 1884, which led to the coining of the terms "Gram-positive" and "Gram-negative."

Bacteria that turn red when stained is called 'Gram-negative' as their cell walls are thinner, allowing the solvent to wash the stains away. However, Bacteria that turn purple when stained are referred to as 'Gram-positive' as their cell walls are too thick for solvents to penetrate.

In the journal, Gram noted, "I have therefore published the method, although I am aware that as yet it is very defective and imperfect; but it is hoped that also in the hands of other investigators it will turn out to be useful," as a modest disclaimer.

Hans Christian Gram died in 1938. However, the staining process he created played a major role in classifying bacteria. The test proved to be widely applicable. More than a century has passed since he first discovered the staining process, but the method continues to be utilised to this day.