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Questions and Answers
Gram staining is a method used in microbiology and bacteriology to classify bacterial species into two large groups. What are these two groups?
Who developed the Gram staining technique?
What is the purpose of adding Lugol's iodine solution in the Gram staining technique?
Which phylum includes well-known genera such as Lactobacillus, Bacillus, and Staphylococcus?
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What type of bacteria possess a thin layer of peptidoglycan between two membranes?
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Which type of bacteria cannot be determined as either gram-positive or gram-negative?
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Which bacteria lack a cell wall around their cell membranes and do not stain by Gram's method?
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Which staining technique is used to differentiate bacterial species into gram-positive and gram-negative groups?
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What is the purpose of the decolorization step in the Gram staining technique?
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Which type of bacteria has a thick mesh-like cell wall made of peptidoglycan and stains purple in the Gram staining technique?
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In a modern microbiology lab, what is the preferred method for bacterial identification?
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Study Notes
Gram Staining Technique
- Classifies bacterial species into two large groups: Gram-positive and Gram-negative
- Developed by Hans Christian Gram
Gram-positive Bacteria
- Have a thick mesh-like cell wall made of peptidoglycan
- Stain purple in the Gram staining technique
- Examples: Lactobacillus, Bacillus, Staphylococcus (belong to the phylum Firmicutes)
Gram-negative Bacteria
- Possess a thin layer of peptidoglycan between two membranes
- Stain pink in the Gram staining technique
Gram Staining Process
- Lugol's iodine solution is added to help the dye bind to the peptidoglycan layer
- Decolorization step is used to remove excess dye from the Gram-negative bacteria
Exceptions
- Some bacteria lack a cell wall and do not stain by Gram's method (e.g. Mycoplasma)
- Some bacteria cannot be determined as either gram-positive or gram-negative (e.g. Mycobacterium)
Modern Microbiology Lab
- Preferred method for bacterial identification is not Gram staining, but rather other methods such as molecular diagnostics and biochemical testing.
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Description
Test your knowledge of Gram staining, a method used in microbiology to classify bacteria into gram-positive and gram-negative groups. Learn about the history and technique of Gram staining in this quiz.
