Research for infection protection

Gram staining

Hans Christian Joachim Gram (1853 - 1938). Danish bacteriologist who developed the method of staining bacteria in 1884
Hans Christian Joachim Gram

Method of staining bacteria developed by Hans Christian Joachim Gram in 1884. For this, the bacteria are stained with alkaline crystal violet for 1 - 3 minutes. After decantation of the staining solution, the bacteria are treated with iodine-potassium iodide producing a water-insoluble complex. Then, this solution is decanted as well. Afterwards, the bacteria are rinsed with alcohol. Results: Gram-positive bacteria retain the blue dye, Gram-negative release it. Gram did not carry out counterstaining with basic fuchsin or safranin as it later would become commonplace.