Quiz 2 Updated Flashcards
(63 cards)
Why do we use the gram stain?
To help us differentiate between gram - and gram + cells.
What are the four reagents used in gram stain?
Crystal violet (primary dye)
Iodine (mordant)
Ethanol (decolorizer)
Safranin (counter stain)
What is the chemistry of crystal violet in gram stain?
The crystal violet binds to all bacteria because it is a cationic dye, attracting to the anionic exterior of the cell
What is the chemistry of iodine in gram stain?
The iodine helps the crystal violet “stick better” to the bacteria by forming a complex
What is the chemistry of ethanol in gram stain?
The ethanol dissolves lipids and since the gram - bacteria have an outer cell membrane, it will get dissolved and flush out the crystal violet
What is the chemistry of safranin in gram stain?
The safranin helps the gram - cells stain pink. Since the ethanol dissolved their color and outer membrane, we need to counterstain so that we can see gram - cells.
What is the structure of gram + bacteria?
We have an inner cell membrane and a thick peptidoglycan layer
What is the structure of gram - bacteria?
We have an inner cell membrane, a thin peptidoglycan layer, and an outer cell membrane
What is the color of gram - and gram+ after staining?
Gram - : pink/red
Gram + : purple
What would happen if safranin was left out?
We would not see the gram - cells
What would happen if ethanol was left out?
We would not be able to differentiate gram - from gram + because the gram - would retain the purple
What would happen if iodine was left out?
It would be harder to differentiate because the crystal violet would wash out from both gram - and gram +
What would happen if the cultures we used in gram stain were old?
It could alter our results because the cell walls would become thin so crystal violet and iodine would not work effectively
What is the acid fast stain? What is its purpose?
The acid fast stain is another differential stain that is used to identify the mycobacterium species based on it’s mycolic acid layer
What is the main pathogen and disease associated with mycolic acid?
Mycobacterium TB and the disease is Tuberculosis
What reagents are used in acid fast stain?
Carbolfushion (primary dye)
Acid- Alcohol (decolorizer)
Methylene blue (counter stain)
Why is mycolic acid a virulence factor?
Because it helps bacteria resist chemical damage, dehydration and antibiotics
What is an endospore?
A specialized structure that some bacteria form when their environment is threatened
Endospores only occur in which 2 genera?
Clostridium and Bacillus
What reagents do we use for endospore stain? What is the name of this method?
Malachite Green (primary dye)
Safranin (counterstain)
This is the Schaeffer-Fulton method.
What is a vegetative state?
When a bacteria is active (without a spore)
What is a capsule?
Can be referred to as glycocalyx and they protect the cell from outside environment
Why are capsules a virulence factor?
They protect bacteria and let them flourish despite the harsh conditions
Why is a capsule stain also called negative stain?
Because in this procedure, we are not actually staining the capsule, we are staining the background and the bacteria.
