Quiz 2 Flashcards
Simple stain (3A)
Consists of one dye that stains a component of the microbial cell
What is the most commonly used basic dye? (3A)
Methylene blue
Why is methylene blue a commonly used dye? (3A)
It dyes the more acidic components of the cell more deeply than less acidic parts of the cell
What are two common things that are smeared with methylene blue? (3A)
Raw milk & throat smears in the diagnosis of diptheria
What yeast was used in exercise 3A?
Saccharomyces cerevisiae
Briefly describe how to prepare a simple stain (3A)
-Place a dot of water on the slide -Smear in a bit of the bacteria/yeast/etc -Let it air dry, then fix it by passing through flame -Apply several drops of methylene blue & let sit for about a minute -Rinse with water, dry, and examine
About how large is a yeast cell? (3A)
7 x 15 microns
Differential stain (3B)
Uses two or more dyes that can be used to categorize cells into groups
What are the four dyes used in a gram stain? (3B)
i) Crystal violet ii) Gram’s iodine iii) Decolorizer iv) Safranin (counter-stain)
What color do gram-positive cells stain? (3B)
Purple – hold onto the crystal violet b/c of the thick peptidoglycan layer
What color do gram-negative cells strain? (3B)
Pink – decolorizer penetrates lipid membrane, but holds the saffranin
Why might a cell be gram-variable? (3B)
-Depending upon how long the culture has been growing, it might appear gram-positive or gram-negative. -For example, many gram-positive bacteria will appear gram-negative in later stages of growth. -Young growths shouldn’t be gram variable (less than 12-18 hrs).
What three bacteria were used in the gram-staining procedure? (3B)
-Staphylococcus epidermis - Gram positive -Bacillus subtilis - Gram variable -Escherichia coli - Gram negative
Briefly describe the gram staining method (3B)
-Apply water to slide, apply bacterial strains to the water, let air-dry, and heat-fix -Stain with crystal violet for ~1 min, rinse w/ water -Stain with iodine for ~1 min, rinse w/ water -Decolorize for 2-5 sec -Stain w/ Safranin for ~30 sec, rinse, dry, & examine
Cell capsule (3C)
-Protects the cell, does not provide any necessary functions though -Often destroyed in some methods of staining -India ink is often used to do a negative stain & stain the background, leaving the cells white so we can see the capsule
Name a genus that contains a capsule (3C)
Klebsiella
Name two genus that make spores (3D)
Bacillus & Clostridium
What are the dormant structures that are made during sporulation called? (3D)
Endospores
What triggers the formation of endospores? (3D)
Usually, lack of nutrients in the environment. Sporulation causes the cells to become dormant & they will become active again once there are more nutrients available
What bacterium was spore-stained in 3D?
Bacillus subtilis -Sub-terminal spore -Gram positive
Briefly describe the spore-staining technique (3D)
-Swab bacterial culture & place whole swab into malachite green, place in boiling water bath ~10 min -Rub swab onto a slide, heat fix -Decolorize with water 2-5 sec -Stain w/ Safranin ~20 sec -Rinse w/ water, dry, & examine
Why would a person want to do a spore stain? (3D)
Can determine size, shape, & position of the spore in the cell. The dye will not penetrate the spore, but it will penetrate the vegetative cell, & the counterstain will colorize the spore
What technique was done on the spore stain? (3E)
Leifson’s technique -Uses a mordant to increase cell size
What kind of flagella did the microbe in 3E have?
Polar monotrichous
