Gram Staining
GRAM STAINING
EXPERIMENT CONDUCTED ON 9/29/2013
Introduction: The Gram stain is a useful stain for identifying and classifying bacteria. The Gram stain is a differential stain that allows you to classify bacteria as either gram positive or gram negative. This gram stain technique was discovered by Hans Christina Gram in 1884. The gram stain procedure separates all bacteria into one of two groups - into gram-negative bacteria which do not stain purple and into gram-positive cells which does stain purple. Bacteria that decolorize easily are called gram-negative, and those that decolorize slowly and retain a primary stain are called gram-positive. The gram staining procedure consists of fixing a colony of bacteria onto a slide and then flooding the colony with various chemicals. First, crystal violet dye was dropped onto the bacterial cells, staining gram-positive cells purple. Iodine was added to fix the violet dye into place and then ethanol was used to wash the dye off the unstained cells. Finally, a red dye called safranin was used to stain any gram-negative cells present so that they were visible. Once the gram stain procedure was complete, the gram-positive bacteria appeared purple under a microscope while gram-negative cells appear pink or red. The purpose of this lab was to differentiate bacteria based on the cell wall and to differentiate whether the bacteria was gram-positive or gram-negative. Gram-negative bacteria do not retain the violet dye and are colored red or pink. “Compared with Gram-positive bacteria, Gram-negative bacteria are more resistant against antibodies because of their impenetrable cell wall. These bacteria have a wide variety of applications ranging from medical treatment to industrial use and Swiss cheese production” (2).
Materials:
The materials used in the lab were four different gram-staining reagents: crystal violet, Gram’s iodine, 70% ethanol and safranin. Also, a wash bottle of
EXPERIMENT CONDUCTED ON 9/29/2013
Introduction: The Gram stain is a useful stain for identifying and classifying bacteria. The Gram stain is a differential stain that allows you to classify bacteria as either gram positive or gram negative. This gram stain technique was discovered by Hans Christina Gram in 1884. The gram stain procedure separates all bacteria into one of two groups - into gram-negative bacteria which do not stain purple and into gram-positive cells which does stain purple. Bacteria that decolorize easily are called gram-negative, and those that decolorize slowly and retain a primary stain are called gram-positive. The gram staining procedure consists of fixing a colony of bacteria onto a slide and then flooding the colony with various chemicals. First, crystal violet dye was dropped onto the bacterial cells, staining gram-positive cells purple. Iodine was added to fix the violet dye into place and then ethanol was used to wash the dye off the unstained cells. Finally, a red dye called safranin was used to stain any gram-negative cells present so that they were visible. Once the gram stain procedure was complete, the gram-positive bacteria appeared purple under a microscope while gram-negative cells appear pink or red. The purpose of this lab was to differentiate bacteria based on the cell wall and to differentiate whether the bacteria was gram-positive or gram-negative. Gram-negative bacteria do not retain the violet dye and are colored red or pink. “Compared with Gram-positive bacteria, Gram-negative bacteria are more resistant against antibodies because of their impenetrable cell wall. These bacteria have a wide variety of applications ranging from medical treatment to industrial use and Swiss cheese production” (2).
Materials:
The materials used in the lab were four different gram-staining reagents: crystal violet, Gram’s iodine, 70% ethanol and safranin. Also, a wash bottle of
References: 1. Department of Natural Sciences & Mathematics. "Gram Staining." The Pearson Custom Library for the Biological Sciences. Boston: Pearson, 2011. 49-51. Print. 2. Gram-negative Bacteria vs Gram-positive Bacteria. (n.d.). - Difference and Comparison. Retrieved from http://www.diffen.com/difference/Gram-negative_Bacteria_vs_Gram- positive_Bacteria