Hans Christian Gram

Hans Christian Gram
Hans Christian Gram
Born	(1853-09-13)13 September 1853 Copenhagen
Died	14 November 1938(1938-11-14) (aged 85) Copenhagen
Residence	Denmark
Fields	Bacteriology
Doctoral advisor	Japetus Steenstrup
Known for	Inventing the Gram stain

Hans Christian Joachim Gram (September 13, 1853 – November 14, 1938) was a Danish bacteriologist noted for his development of the Gram stain.

Gram was the son of Frederik Terkel Julius Gram, a professor of jurisprudence, and Louise Christiane Roulund.

Gram studied at the University of Copenhagen and was an assistant in botany to the zoologist Japetus Steenstrup. His study of plants introduced him to the fundamentals of pharmacology and the use of the microscope.

Gram entered medical school in 1878 and graduated in 1883. He travelled throughout Europe between 1878 and 1885. In Berlin, in 1884, he developed a method for distinguishing between two major classes of bacteria. This technique, the Gram stain, continues to be a standard procedure in medical microbiology.

In 1891, Gram taught pharmacology, and later that year was appointed professor at the University of Copenhagen. In 1900, he resigned his chair in pharmacology to become professor of medicine.

The work that gained Gram an international reputation was his development of a method of staining bacteria, to make them more visible under a microscope. The stain later played a major role in classifying bacteria. Gram was a modest man, and in his initial publication he remarked, "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." A Gram stain is made using a primary stain of crystal violet and a counterstain of safranin. Bacteria that turn purple when stained are called 'Gram-positive', while those that turn red when counterstained are called 'Gram-negative'.