Then we immediately rinsed with distilled water) Cover the smear with safranin and wait for 1 min and then wash with water and blot carefully with tissue paper. (It is important not to over decolorize otherwise Gram (+)’s will lose the violet stain. The crystal violet will wash off the smear, so we stopped washing till the smear is colorless. Allow 95% ethanol to flow over the smear using dropper. Then pour off the dye and rinse gently with distilled water. Pour crystal violet and rinse gently with distilled water and then cover the smear with iodine for 1 min. Dry smear, and cover the bacteria on the slid with crystal violet and wait for 1 min. Remove a loopful of NB which contain E.coli and P.vulgaris and placed it on different slides separately and allow it to air dry. Our group (#7) used two of them: Escherichia coli and Proteus vulgaris.
These are: Staphylococcus aureus, Enterobacter aerogenes, Bacillus substilis, Salmonella anatum, Escherichia coli, Proteus vulgaris. To learn dyes used at different staining methods in differential staining Procedure: A) Gram Staining In this procedure different types of bacteria are used throughout the laboratory. Purpose: To learn what is differential staining and its purposes To perform three types of differential staining: Gram staining, Endospore staining and capsule staining To understand their value when used to stain clinical specimen To understand the different characteristics of bacteria and thus the differentiation in staining To understand the basic characteristic of Gram (+) and Gram(-) bacteria and distinguish between them To be familiar with the importance of endospores and capsule in bacteria To have a background of the mechanisms of the dyes used in microbiological studies.
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