Who was Hans Christian Gram, today’s Google Doodle

Born in Copenhagen in 1853, he discovered a procedure to identify families of bacteria and evaluate the most effective treatment to fight infection

If today it is possible to identify the various species of bacteria present on Earth, it is also thanks to him.

We are talking about Hans Christian Gram, Danish physician, microbiologist and pathologist, whose 166th birthday is today. A special date, in short, that Google wanted to celebrate in its own way: dedicating a doodle (the images created by various artists who, periodically, replace the words "Google" on the home page of the search engine) and giving him a day of well-deserved celebrity. As mentioned, in fact, it is thanks to this Danish scientist if today it is possible to identify the families of bacteria in a culture and thus identify the most suitable antibiotic treatment.

The discovery of the Danish microbiologist, born in Copenhagen in 1853 and died in the Danish capital in 1938, happened by chance, or almost. In 1884, while analyzing some samples of lung tissue, Gram noticed that some bacterial cells reacted in a particular way when treated with basic dyes. In particular, bacterial cells took on a more intense coloration if they were in contact with a crystal violet dye, then they were treated with an iodine solution and finally decolorized with ethyl alcohol. Other types of bacteria, however, did not have the same chemical reaction, thus assuming less intense coloration. The bacteria that react to the treatment are therefore defined Gram positive (or Gram+); those "immune" to the staining are instead called Gram negative (or Gram-).

This procedure became famous with the name of Gram's method and, as already mentioned, is still used today in laboratory analysis to recognize the family to which the bacteria in culture belong. This process therefore allows to evaluate which antibiotic to use to treat the infection that afflicts the patient.