Bacteria Classification by Gram Staining Essay

814 Words4 Pages
Bacteria Classification By Gram Staining

Presented By : Karim A. Zaklama 92-1509 Sci. 453-01


To test a sample of laboratory prepared bacteria and categorise it according to Christian's gram positive and gram negative classes and also by viewing it under a high powered microscope and oil immersions; classify its shape and note any special characteristics.


Bacteria was categorised into two groups in 1884 by the Danish
Bacteriologist Christian, gram positive and gram negative by a staining technique where the ability to avoid de-coloration of Crystal Violet solution by alcohol would render the category
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11. Leave the slide to air dry.

B. Examination:

1. Place the slide under microscope on low powered lens. 2. Move the slide using the apparatus until the sample can be seen as a blur under the microscope.
3. Focus the lens to ensure that there is a sample directly under the lens. 4.
Move to higher powered lens, repeat step 3. 5. Move to higher powered lens, repeat step 3 6. Move microscope aside and add Oil immersion, leave for a few seconds and re-examine the slide.

Note Shape and colour and any other observations.

Results and Observations:

It was evident by visual examination that the alcohol was de-colouring or a least partially de-colouring the bacteria. The sample appeared a dark pink or close to violet by the naked eye; a microscope was needed to ensure results. Under the low powered microscope shades of pink were noted. Under the medium power, the shades were more clear but no shape could be made out. Under the high powered microscope clumps of pink rod (bacilli) shaped bacteria cells could be observed. Under Oil Immersion and high powered lens the cells could seen more spaced out and thus a clearer indication of the pink colour, bacilli shape and spores could be made out in the individual cells.


The Shape was noted as Bacilli (Rod-like) shaped cells; a gram variable shape, distinct in either Gram Negative or Gram positive bacteria. The final colour of the cells were stained pink by
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