MCB 2610 Lab Practical
Gram positive bacteria do not retain CV when gram stained, so they appear pink after counter-staining
with safranin. T/F - False. They do retain crystal violet and appear purple
Complex media is made with precise chemical composition. T/F - False. Complex media has
unknown composition
______ is an opportunistic pathogen that causes staph infections. - Staphylococcus aureus
A durham tube is included in the LT broth tubes to detect _________, a byproduct of lactose
fermentation - gas production
Brownian motion is the purposeful movement of microorganisms. T/F - False. It is random
vibrations of organisms coming into contact with water molecules
Cells that do not retain crystal violet and appear pink are said to be - Gram negative
Cells that retain crystal violet and appear purple are - Gram positive
Coliforms are a subgroup of enteric bacteria classified by their ability to ferment which sugar? -
Lactose
Define generation time - The amount of time it takes a population to double
Eosin-methylene blue (EMB) agar is used as a confirmed test for coliforms. T/F - True
Fomite examples - cell phone, table, door knob
, Generation time is calculated in log phase. T/F - True
Gram positive bacteria have a thick peptidoglycan layer which retains safranin and appears pink. T/F -
False. Retains crystal violet and appears purple.
Gram staining steps - 1. apply bacterial sample to glass slide
2. heat fix slide
3. crystal violet solution (1 min)
4. rinse with water
5. gram's iodine (mordant for CV) (1 min)
6. rinse
7. decolorizer (alcohol wash) (10 sec)
8. rinse
9. safranin (counter stain) 1 min
10. rinse with water and pat dry
gram (+) : purple
gram (-) : pink
Gram stains and spore stains are examples of simple stains. T/F - False. These are differential
staining techniques
Heat staining causes sporulation. T/F - False.
How is casein hydrolysis detected? - Clearing zone around colonies
How many times do you get culture from the tube while performing a T streak? - 1
Is LT broth selective, differential or both? - Both
Gram positive bacteria do not retain CV when gram stained, so they appear pink after counter-staining
with safranin. T/F - False. They do retain crystal violet and appear purple
Complex media is made with precise chemical composition. T/F - False. Complex media has
unknown composition
______ is an opportunistic pathogen that causes staph infections. - Staphylococcus aureus
A durham tube is included in the LT broth tubes to detect _________, a byproduct of lactose
fermentation - gas production
Brownian motion is the purposeful movement of microorganisms. T/F - False. It is random
vibrations of organisms coming into contact with water molecules
Cells that do not retain crystal violet and appear pink are said to be - Gram negative
Cells that retain crystal violet and appear purple are - Gram positive
Coliforms are a subgroup of enteric bacteria classified by their ability to ferment which sugar? -
Lactose
Define generation time - The amount of time it takes a population to double
Eosin-methylene blue (EMB) agar is used as a confirmed test for coliforms. T/F - True
Fomite examples - cell phone, table, door knob
, Generation time is calculated in log phase. T/F - True
Gram positive bacteria have a thick peptidoglycan layer which retains safranin and appears pink. T/F -
False. Retains crystal violet and appears purple.
Gram staining steps - 1. apply bacterial sample to glass slide
2. heat fix slide
3. crystal violet solution (1 min)
4. rinse with water
5. gram's iodine (mordant for CV) (1 min)
6. rinse
7. decolorizer (alcohol wash) (10 sec)
8. rinse
9. safranin (counter stain) 1 min
10. rinse with water and pat dry
gram (+) : purple
gram (-) : pink
Gram stains and spore stains are examples of simple stains. T/F - False. These are differential
staining techniques
Heat staining causes sporulation. T/F - False.
How is casein hydrolysis detected? - Clearing zone around colonies
How many times do you get culture from the tube while performing a T streak? - 1
Is LT broth selective, differential or both? - Both
