CMMB 343 lab final exam questions and answers 2024-2025 with complete solution
How to do .....
BHI stant
How to interpret results? - Slanted BHI agar in a test tube
Inoculate with the sample
Will see growth on surface of agar if aerobic microbe.
Fissures and cracks below surface if able to ferment.
Deep shake culture - Innoculate a loop of sample in molten agar and rotate in hands to
mix.
If fissures below the surface, can ferment.
If no fissures, cannot ferment.
Thioglycollate Medium - Pipette some liquid culture to the bottom of the tube BELOW the pink layer. Turbidity will show where the microbes are able to survive. This is based on the oxygen gradient within the tube.
A facultative aerobe will show what results in a thioglycollate tube? - Turbidity all throughout the tube, but a bit more turbid in the top segment.
What is the upper pink layer of a thioglycollate tube? - oxygenated layer
When they say "oxygen is a nutrient" what is meant? - It is needed as the final e- acceptor in the ETC to generate ATP.
Name 2 enzymes that are part of respiration. What 2 tests can be used to detect them? - cytochrome c oxidase
Oxidase test
catalase Catalase test
How to do and interpret....
oxidase test - -hold the RED end of oxidase stick
-put BROWN end into cells
Negative result: colourless
Positive result: blue
How to do and interpret....
catalase test - Add 2 drops of hydrogen peroxide to a colony on an agar plate
if bubbling, catalase is present
What are the gas bubbles you see in a positive catalase test? - O2
The enzyme catalase converts the added Hydrogen Peroxide to ___________ and ___________. - water and oxygen gas
How to do and interpret....
H&L glucose test - use 2 H&L glucose test tubes. These have glucose as a carbon source in the medium.
Shows if and where the species can use glucose as a carbon source.
Inoculate both and add a layer of mineral oil to the top of one of them. POSITIVE = turns yellow
NEGATIVE = stays green
What does it mean if the top layer turns blue in an H&L glucose test? - Negative result
Colour change occurred due to the organisms using peptones in the medium and excreting alkaline end products. NOT carbohydrate utilization.
How to do and interpret...
H&L lactose test - use 2 H&L lactose test tubes.
These have lactose as a carbon source in the medium.
Shows if the species can ferment lactose.
Inoculate both and add a layer of mineral oil to the top of one tube.
How to do .....
BHI stant
How to interpret results? - Slanted BHI agar in a test tube
Inoculate with the sample
Will see growth on surface of agar if aerobic microbe.
Fissures and cracks below surface if able to ferment.
Deep shake culture - Innoculate a loop of sample in molten agar and rotate in hands to
mix.
If fissures below the surface, can ferment.
If no fissures, cannot ferment.
Thioglycollate Medium - Pipette some liquid culture to the bottom of the tube BELOW the pink layer. Turbidity will show where the microbes are able to survive. This is based on the oxygen gradient within the tube.
A facultative aerobe will show what results in a thioglycollate tube? - Turbidity all throughout the tube, but a bit more turbid in the top segment.
What is the upper pink layer of a thioglycollate tube? - oxygenated layer
When they say "oxygen is a nutrient" what is meant? - It is needed as the final e- acceptor in the ETC to generate ATP.
Name 2 enzymes that are part of respiration. What 2 tests can be used to detect them? - cytochrome c oxidase
Oxidase test
catalase Catalase test
How to do and interpret....
oxidase test - -hold the RED end of oxidase stick
-put BROWN end into cells
Negative result: colourless
Positive result: blue
How to do and interpret....
catalase test - Add 2 drops of hydrogen peroxide to a colony on an agar plate
if bubbling, catalase is present
What are the gas bubbles you see in a positive catalase test? - O2
The enzyme catalase converts the added Hydrogen Peroxide to ___________ and ___________. - water and oxygen gas
How to do and interpret....
H&L glucose test - use 2 H&L glucose test tubes. These have glucose as a carbon source in the medium.
Shows if and where the species can use glucose as a carbon source.
Inoculate both and add a layer of mineral oil to the top of one of them. POSITIVE = turns yellow
NEGATIVE = stays green
What does it mean if the top layer turns blue in an H&L glucose test? - Negative result
Colour change occurred due to the organisms using peptones in the medium and excreting alkaline end products. NOT carbohydrate utilization.
How to do and interpret...
H&L lactose test - use 2 H&L lactose test tubes.
These have lactose as a carbon source in the medium.
Shows if the species can ferment lactose.
Inoculate both and add a layer of mineral oil to the top of one tube.
