Purpose Statement:
The purpose of this experiment was to determine the Gram stain of the certain slant cultures we used in class, Escherichia coli and Staphylococcus aureus, under a microscope. Since it is the most important staining procedure in microbiology, it is used to distinguish between gram-positive and gram-negative organisms. The gram-positive cells stain purple, and the gram-negative stain a pinkish color. This staining is a differential stain that allows is used to identify the changes between organisms or differences within the same organism.
Theory and Background:
The Gram staining method was named after the Danish bacteriologist, Hans Christian Gram, in 1882. This method is now one of the most important staining procedures in microbiology.
Steps of the Gram stain:
Reagents:
• Escherichia coli (slant culture)
• Staphylococcus aureus (slant culture)
• Crystal violet (primary stain)
• Iodine solution (Gram’s iodine)
• Decolorizer (ethanol)
• Safranin (counterstain)
• Water (in squirt bottle)
Prepare a mixed smear using slant cultures:
1. Take two …show more content…
Observe each slide under the microscope, determining whether the bacteria are gram-positive which is stained purple or gram-negative which is stained red.
Results:
Through the process of the experiment, e. coli was determined to be gram-negative and S. aureus was gram-positive. By looking through the microscope at the positive staining, the appearance of the cell seemed to be colored by the dye and the background was not stained. The crystal violet made the gram-positive a thick purple layer, which made it easier to see looking through the microscope. When looking at the negative staining, the appearance of the cell seemed clear and colorless, or a faint pink color. The crystal violet made a thin membrane layer so it was harder to see it through the microscope.
The purpose of this experiment was to determine the Gram stain of the certain slant cultures we used in class, Escherichia coli and Staphylococcus aureus, under a microscope. Since it is the most important staining procedure in microbiology, it is used to distinguish between gram-positive and gram-negative organisms. The gram-positive cells stain purple, and the gram-negative stain a pinkish color. This staining is a differential stain that allows is used to identify the changes between organisms or differences within the same organism.
Theory and Background:
The Gram staining method was named after the Danish bacteriologist, Hans Christian Gram, in 1882. This method is now one of the most important staining procedures in microbiology.
Steps of the Gram stain:
Reagents:
• Escherichia coli (slant culture)
• Staphylococcus aureus (slant culture)
• Crystal violet (primary stain)
• Iodine solution (Gram’s iodine)
• Decolorizer (ethanol)
• Safranin (counterstain)
• Water (in squirt bottle)
Prepare a mixed smear using slant cultures:
1. Take two …show more content…
Observe each slide under the microscope, determining whether the bacteria are gram-positive which is stained purple or gram-negative which is stained red.
Results:
Through the process of the experiment, e. coli was determined to be gram-negative and S. aureus was gram-positive. By looking through the microscope at the positive staining, the appearance of the cell seemed to be colored by the dye and the background was not stained. The crystal violet made the gram-positive a thick purple layer, which made it easier to see looking through the microscope. When looking at the negative staining, the appearance of the cell seemed clear and colorless, or a faint pink color. The crystal violet made a thin membrane layer so it was harder to see it through the microscope.