GRAM STAIN Meaning and
Definition
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Gram stain is a laboratory technique used in microbiology to classify and differentiate bacteria into two major categories based on their cell wall composition, Gram-positive and Gram-negative. It was developed by the Danish bacteriologist Hans Christian Gram in 1884 and remains one of the most widely used staining techniques in the field.
The procedure involves a series of sequential steps. Initially, a bacterial sample is fixed onto a glass slide, then it is stained with crystal violet, a purple dye, followed by iodine, which forms a complex with the crystal violet. The slide is then washed with a decolorizing agent, usually alcohol or acetone, that removes the stain from Gram-negative bacteria while retaining it in Gram-positive bacteria. Finally, a counterstain, such as safranin or fuchsine, is applied to the slide, resulting in the visualization of the Gram-negative bacteria in pink or red color and the Gram-positive bacteria in dark purple or black color.
The Gram stain technique allows microbiologists to quickly differentiate between the two major groups of bacteria, as Gram-positive bacteria have a thick peptidoglycan layer in their cell wall which retains the crystal violet stain, while Gram-negative bacteria have a thinner peptidoglycan layer which is decolorized, allowing the counterstain to take effect. This distinction is valuable for several reasons, including guiding appropriate antibiotic treatment, identifying potential pathogens, and aiding in the taxonomical classification of bacteria.
Common Misspellings for GRAM STAIN
- fram stain
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- bram stain
- hram stain
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Etymology of GRAM STAIN
The word "Gram stain" is derived from the name of its inventor, Hans Christian Gram. Gram was a Danish bacteriologist who developed the staining technique in 1884 while working at the University of Copenhagen. The technique, known as the Gram staining method, allows bacteria to be classified into two groups: Gram-positive (which retain the violet color of the dye) and Gram-negative (which do not retain the stain and appear red or pink). The word "stain" refers to the process of coloring the bacteria for microscopic examination.
