What is meant by gram reaction?

Gram reaction A reaction obtained when bacteria are subjected, in the laboratory, to a certain staining procedure called the Gram stain or Gram’s stain (after the Danish scientist Christian Gram (1853–1938) who first devised the technique in 1884).

What is the gram reaction on microbiology?

Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents. The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet.

What is the gram reaction of a cell?

Gram’s method involves staining the sample cells dark blue, decolorizing those cells with a thin cell wall by rinsing the sample, then counterstaining with a red dye. The cells with a thick cell wall appear blue (gram positive) as crystal violet is retained within the cells, and so the red dye cannot be seen.

How do you find the gram reaction?

Gram Stain Identification

1. Apply the first stain (a purple stain called crystal violet) to a heat-fixed smear of a bacterial culture.
2. Apply iodine on top of the crystal violet.
3. Wash the cells with alcohol or acetone.
4. Stain the cells again (counterstain) with a red dye, either safranin red or basic fuchsin.

Why is it called Gram stain?

The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique. Gram staining differentiates bacteria by the chemical and physical properties of their cell walls. Gram-negative cells have a thinner peptidoglycan layer that allows the crystal violet to wash out on addition of ethanol.

What is Gram stain Class 11?

Answer. 113.1k+ views. 4 likes. Hint: Gram staining is a procedure which is usually based upon the capability of the bacterial cell wall to preserve the crystal violet dye when treated with solvent.

What is difference between gram positive and negative?

Gram positive bacteria have a thick peptidoglycan layer and no outer lipid membrane whilst Gram negative bacteria have a thin peptidoglycan layer and have an outer lipid membrane.

What Gram stain means?

A Gram stain is a test that checks for bacteria at the site of a suspected infection such as the throat, lungs, genitals, or in skin wounds. When the stain combines with bacteria in a sample, the bacteria will either stay purple or turn pink or red. If the bacteria stays purple, they are Gram-positive.

What are the steps of a Gram stain?

The performance of the Gram Stain on any sample requires four basic steps that include applying a primary stain (crystal violet) to a heat-fixed smear, followed by the addition of a mordant (Gram’s Iodine), rapid decolorization with alcohol, acetone, or a mixture of alcohol and acetone and lastly, counterstaining with …

What are the 4 steps of Gram staining?

What is the principle behind Gram staining?

The basic principle of gram staining involves the ability of the bacterial cell wall to retain the crystal violet dye during solvent treatment. Gram-positive microorganisms have higher peptidoglycan content, whereas gram-negative organisms have higher lipid content.

What is Gram-positive and negative?

In 1884, a bacteriologist named Christian Gram created a test that could determine if a bacterium had a thick, mesh-like membrane called peptidoglycan. Bacteria with thick peptidoglycan are called gram positive. If the peptidoglycan layer is thin, it’s classified as gram negative.