Gram Staining A Magna Academy BioMed Club storyline

Welcome to our BioMed Club storyline. BioMed Club is an enrichment offer for Science students studying at Magna Academy Poole. The Club meets every week and investigates new and interesting Science techniques.

Gram staining is a method of staining that is used to distinguish and classify bacterial species into two large groups, called gram-positive and gram-negative. The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique.

The technique is named after the Danish bacteriologist Hans Christian Gram (1853-1958), who first developed it.

Gram developed this technique while working in the morgue of the city hospital in Berlin in 1884. He devised his technique to make bacteria more visible in stained sections of lung tissue. He published his method in 1884, and included in his short report the observation that the typhus bacillus did not retain the stain

His technique has since been further developed for the purpose of distinguishing one type of bacterium from another.

Miss Poulton's BioMed Club in action learning about Gram Staining

Gram staining differentiates bacteria by the chemical and physical properties of their cell walls.

The technique detects peptidoglycan, which is present in the cell wall of Gram-positive bacteria.

Gram-negative cells also contain peptidoglycan but a very small layer of it that is dissolved when the alcohol is added. This is why the cell loses its initial colour from the primary stain.

The Gram-positive bacteria retain the crystal violet dye and are stained violet. The Gram-negative bacteria do not.

After washing, a counter-stain is added that will stain Gram-negative bacteria a pink colour. Both Gram-positive bacteria and Gram-negative bacteria pick up the counter-stain.

The counter-stain is unseen on Gram-positive bacteria because of the darker crystal violet stain.

Here is a short video from YouTube that helps explain the process step-by-step.


All photography (c) Magna Academy Poole 2017

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