Microbiology Lab Final Questions and Answers Graded A+
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Course
Microbiology Lab
Institution
Microbiology Lab
Microbiology Lab Final Questions and
Answers Graded A+
What is the appearance of a positive MacConkey agar test for lactose fermenters?
Pink colonies due to acid production from lactose fermentation.
What is the purpose of using a selective medium like EMB agar?
To isolate and differenti...
Microbiology Lab Final Questions and
Answers Graded A+
What is the appearance of a positive MacConkey agar test for lactose fermenters?
✔✔Pink colonies due to acid production from lactose fermentation.
What is the purpose of using a selective medium like EMB agar?
✔✔To isolate and differentiate Gram-negative bacteria, especially enteric bacteria.
What is the main characteristic of a positive phenol red test?
✔✔A color change to yellow indicates acid production from sugar fermentation.
What does the presence of a clear zone around a bacterial colony on an amylase test plate
indicate?
✔✔The bacterium produces amylase, which breaks down starch into simpler sugars.
What is the primary role of a bacterial endospore?
✔✔To protect the bacterium during harsh environmental conditions and ensure survival.
1
,What does a positive H2S test result look like?
✔✔Black precipitate in the medium, indicating the production of hydrogen sulfide.
What is the function of a bacterial capsule?
✔✔To protect the bacterium from phagocytosis by host immune cells.
What does a positive gelatin hydrolysis test indicate?
✔✔The bacterium produces gelatinase, which liquefies the gelatin medium.
What is the purpose of an oxidase test in identifying bacteria?
✔✔To determine if the bacterium possesses cytochrome c oxidase, an enzyme involved in
aerobic respiration.
What does a positive nitrate reduction test show?
✔✔A red color indicates that nitrate was reduced to nitrite or nitrogen gas.
What is the result of a positive VP (Voges-Proskauer) test?
✔✔A red color appears after the addition of reagents, indicating acetoin production.
2
, What is the appearance of a positive urease test in the presence of urease-producing bacteria?
✔✔Pink color change due to ammonia production from urea hydrolysis.
What is the primary use of a selective medium such as MacConkey agar?
✔✔To select for Gram-negative organisms and differentiate lactose fermenters.
What is the significance of the catalase test?
✔✔To determine if a bacterium produces catalase, which breaks down hydrogen peroxide into
water and oxygen.
What does a positive coagulase test indicate?
✔✔The bacterium produces coagulase, an enzyme that causes plasma to clot.
What does a positive indole test reveal about a bacterium’s metabolism?
✔✔The bacterium produces indole from tryptophan metabolism.
What does a positive motility test result look like?
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