Master Microbiology with 200 free flashcards. Study using spaced repetition and focus mode for effective learning in Science.
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What is the basic structural difference between Gram-positive and Gram-negative cell walls?
Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane; Gram-negative bacteria have a thin peptidoglycan layer plus an outer membrane containing lipopolysaccharide (LPS).
Q · 1 of 200
What is the basic structural difference between Gram-positive and Gram-negative cell walls?
Q · 2 of 200
What color do Gram-positive bacteria appear after Gram staining?
Q · 3 of 200
What color do Gram-negative bacteria appear after Gram staining?
Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane; Gram-negative bacteria have a thin peptidoglycan layer plus an outer membrane containing lipopolysaccharide (LPS).
Purple/violet (retain crystal violet-iodine complex).
Pink/red (crystal violet is washed out by decolorizer; counterstained with safranin).
1) Crystal violet (primary stain) 2) Gram's iodine (mordant) 3) Alcohol/acetone decolorizer 4) Safranin (counterstain).
Lipopolysaccharide (LPS), specifically its lipid A component.
A polymer unique to Gram-positive cell walls that extends through the peptidoglycan and contributes to virulence and immune stimulation.
Peptidoglycan (murein), made of alternating NAG and NAM sugars cross-linked by peptide chains.
Lysozyme.
Mycoplasma.
Mycolic acid, a waxy lipid layer.
Ziehl-Neelsen (acid-fast) stain, which appears bright red/pink against a blue background.
Motility/locomotion, propelled by rotation of the flagellar motor.
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