Gram Positive and Gram Negative Bacteria




This method of staining can be trace back to 1884 when a man called Christian Gram explained this method as one of the method that is very important staining in routine bacteriology. On his explanation, he group bacteria into two, which are; Gram positive & Gram negative bacteria. This grouping is based on the color and de colorization of the bacteria when stained by gram staining technique, acetone, alcohol, aniline oil are the reagent used for de colorization. Before the reagent is put to used, staining of the smear with methylene blue, crystal violet, gentian violet, are used for staining and where treated with iodine. On his method he explain that those organism that resist change of colour after been stain with dye; safranin, but retain the primary color, i.e crystal violet or methelene blue, they are called Gram positive, while those organism that resist primary stain but retain color of safranin or other dyes, this organism are called Gram negative.

Gram-positve                                                                      Gram-negative

Bacillus species                                                                     Coliforms

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Mycobacteria                                                                           Neisseria

Clostridia                                                                                 Vibrio’s


This method of staining has been extensible studies, but seems so difficult to understand. However other method exist that aid the examination of the organism.

Therefore, after Gram staining another method where employed for organism examination, because not all of this organism can be demonstrated by using only Gram staining principle i.e. Such as acid fast bacilli method, this method consist of Ziehl Neelson, Auramine staining etc.

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