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MCB2010 Final Exam (1)
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MCB2010 Final Examdifferential stain - ANS-react differently with different kinds of bacteria and thus can be
used to distinguish them
How many dyes for differential stain? - ANS-2 dyes (basic w/ contrasting color)
ex. Crystal violet & safranin or Carbolfuschin & methylene blue
What does differential staining stain? - ANS-Eubacteria Kingdom
Differential Staining Steps - ANS-After smear prep...
1. Apply first dye (primary stain)
2. Apply mordant (secures color to stain)
3. Apply decolorizing agent (removes dyes from some cells)
4. Rinse w/ water. Add counterstain safranin.
Chemical groups of dyes in differential staining - ANS-basic dyes
Gram stain results - ANS-Purple (primary dye) = positive
Red (counterstain) = negative
Why bacteria have a reaction to gram stain? - ANS-- due to the cell wall
- cell wall = peptidoglycan (disaccharide+protein)
- archaea can't be stained because the cell wall lacks peptidoglycan
Why do bacteria react differently to gram stain? - ANS-- different layers of peptidoglycan
(thicker)
Gram's Bacteria - ANS-- streptococcus pneumonia (+)
- Klebsiella pneumonia (-)
Peptidoglycan - ANS-Gram-positive bacteria cell walls have multiple layers, while
Gram-negative bacteria cell walls have a single layer of peptidoglycan covered by a
thick outer-membrane of lipids
Teichoic Acids - ANS-exclusive component of Gram-positive bacterial cell wall( about
10%). Sometimes, it extends to the plasma membrane as Lipoteichoic acid
lipotechoic - ANS-in gram positive, linked to plasma membrane
, Lipo-polysaccharides - ANS-outer membrane of gram - bacteria
Peptidoglycan in Gram + - ANS-90-95%
Peptidoglycan in Gram - - ANS-15%
Effect of Antibiotics - ANS-kill gram + bacteria, cannot kill gram - bacteria
Carl Weiger - ANS-added counterstain procedure to Gram stain to reveal bacteria in the
cells of infected tissue
Periplasmic Space - ANS-The space between the inner and outer cell membranes in
Gram-negative bacteria
What toxins are produced by Gram positive bacteria? - ANS-Exotoxins
What Toxins are produced by Gram negative bacteria? - ANS-Endotoxin and exotoxins
Flagellar Structure of Gram positive bacteria - ANS-2 rings in basal body
Flagellar Structure of Gram negative bacteria - ANS-4 rings in basal body
Gram positive susceptibility to Penicillin - ANS-High
Gram negative susceptibility to Penicillin - ANS-Low
Gram positive susceptibility to Anionic Detergents - ANS-High
Gram negative susceptibility to Anionic Detergents - ANS-Low
Vital Characteristics of Microbial Life - ANS-1. Irritability
2. Nutrition
3. Growth
4. Reproduction
5. Movement
6. Respiration
7. Excretion (getting rid of metabolic waste)
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