Characterizing Bacteria Using Gram Staining
Our Bacterial Gram Staining kit is supplied with three strains of bacteria and all the necessary prealiquoted components to carry out the Gram staining to determine Gram positive and negative bacteria.
The Gram staining method was first described in 1844 by the Danish bacteriologist Hans Christian Gram, after whom the test was named. The Gram staining test for bacteria is one of the most important tests in microbiology and is often one of the first tests performed in the identification of bacteria.
Gram staining separates the three shape groups into two color groups: purple or red coccus, bacillus, or spirillum. Gram-stained samples can be separated into one of these six groups.
The purple or red coloration is determined by the bacterium’s cell wall type. Bacteria that have a thick cell wall of peptidoglycan with a relatively low lipid content retain a purple stain, called crystal violet, and turn dark purple in color. These are called Gram+ bacteria because they take up and retain the crystal violet stain.
Bacteria that have a cell wall with a relatively high lipid content (and lower peptidoglycan content) lose the purple color during de-colorization and must be stained with a contrasting red counterstain, called safranin. These bacterial cells appear reddish-pink and are called Gram– bacteria because they have not retained the purple color of the crystal violet stain.
When properly Gram-stained, Kocuria rhizophilia appears as purple spheres (Gram+ cocci) and Bacillus subtilis appears as light red rods (Gram– bacilli) at 400-1000X magnification. These two bacteria will be used as positive controls for comparison when Gram-staining a sample of E. coli.
Our Bacterial Gram Staining kit is supplied with three strains of bacteria and all the necessary components to carry out the Gram staining.
Supplied with components needed for hands-on experimentation for eight workstations of 2-4 students or 16-32 students.
- Stain three strains of bacteria with Gram stain.
- Understand the principle of Gram staining.
- Role of Gram stain in clinical diagnostics.
This laboratory activity is adapted from “Laboratory 4l: Characterizing E. coli Using a Light Microscope and Gram Staining” from Biotechnology: Laboratory Manual by Ellyn Daugherty. For more information about the program, please visit www.emcp.com/biotechnology. This kit is produced under license from Paradigm Publishing, Inc., a division of New Mountain Learning.
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