THE AMERICAN UNIVERSITY IN CAIRO
SCIENCE 453 : BIOLOGY FOR ENGINEERS
BACTERIA CLASSIFICATION BY GRAM STAINING
Presented By : Karim A. Zaklama
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 of gram positive, and gram negative if the bacteria is de-coloured. This could be noted by the final colour of the bacteria: a violet colour where Gram positive and a pink colour of the Safranin added pending the de-colouring process.
1. Bacteria Sample
2. Microscope Slide
3. Gram Staining Kit and Wash Bottles
a. Crystal Violet Solution
b. Iodine Solution
c. 95% Ethyl Alcohol
e. Distilled Water
4. Bibulous Blotting Paper
A. Preparation :
1. Bacteria is cultivated on agar jelly in an incubator at 25ÃÂ°C for 24 hours.
2. Obtain a microscope slide and with a toothpick, smear a thin coat of the bacteria sample onto the slide
3. Cover the smear with a drop Crystal Violet and leave standing for 20 seconds
4. Wash off the stain with distilled water; drain and blot off the excess with bibulous paper.
5. Apply Gram's Iodine on the smear and leave to stand for 1 minute.
6. Drain the excess iodine and apply 95% Ethyl alcohol for 20 second duration or till the alcohol runs clearly from the slide.
7. The smear...