Microbiology Lab Mid Term Study Guide Questions with Verified Solutions
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Course
Microbiology Lab Mid
Institution
Microbiology Lab Mid
Microbiology Lab Mid Term Study Guide
Questions with Verified Solutions
What is the purpose of inoculating a microbiological medium with a sample?
To introduce microorganisms for growth and observation.
What does the term "aseptic technique" refer to in microbiology?
Methods used to prev...
Microbiology Lab Mid Term Study Guide
Questions with Verified Solutions
What is the purpose of inoculating a microbiological medium with a sample?
✔✔ To introduce microorganisms for growth and observation.
What does the term "aseptic technique" refer to in microbiology?
✔✔ Methods used to prevent contamination during handling of cultures and samples.
Why is it necessary to flame the neck of a culture tube before and after use?
✔✔ To sterilize the opening and prevent contamination from airborne microorganisms.
What is the purpose of a streak plate technique?
✔✔ To isolate individual bacterial colonies from a mixture.
Why is it important to use fresh bacterial cultures when performing a Gram stain?
✔✔ To ensure accurate results since older cultures may not retain the Gram-positive reaction.
1
,What does the presence of a yellow color in a phenol red broth indicate?
✔✔ That the bacteria have fermented the carbohydrate and produced acid.
What is the purpose of the oxidase test?
✔✔ To detect the presence of cytochrome c oxidase in bacteria.
What does a positive result in the catalase test look like?
✔✔ Bubbling or fizzing when hydrogen peroxide is added to the bacterial culture.
What type of media is MacConkey agar, and what does it differentiate?
✔✔ It is a selective and differential medium that differentiates lactose fermenters from non-
fermenters.
What is the difference between a selective and a differential medium?
✔✔ Selective media inhibit the growth of certain microorganisms, while differential media allow
for the differentiation of organisms based on specific characteristics.
Why do you use a Durham tube in a fermentation test?
2
,✔✔ To capture gas produced by bacteria during fermentation.
What is the purpose of the endospore stain?
✔✔ To identify bacteria that can form endospores, a structure resistant to harsh conditions.
What color will endospores appear after an endospore stain?
✔✔ Green, as the primary stain malachite green stains the spores.
What is the purpose of using an agar slant in microbiology?
✔✔ To provide a solid growth surface for the long-term cultivation and storage of
microorganisms.
How do you determine the motility of a bacterium using a SIM medium?
✔✔ By observing whether the bacteria spread throughout the agar, indicating movement.
What type of bacteria would show a positive result for hydrogen sulfide production on SIM
medium?
✔✔ Bacteria that produce hydrogen sulfide will form black precipitates in the medium.
3
, Why are bacterial cultures incubated at specific temperatures?
✔✔ To provide optimal growth conditions for different types of bacteria, based on their
preferred temperature range.
What is the primary function of a biosafety cabinet in a microbiology lab?
✔✔ To provide a controlled environment that minimizes the risk of contamination and exposure
to hazardous materials.
What is the purpose of using a Bunsen burner in the microbiology lab?
✔✔ To sterilize tools, like inoculating loops, and create an aseptic environment by producing a
sterile flame.
What is the main purpose of performing a Gram stain in microbiology?
✔✔ To classify bacteria as Gram-positive or Gram-negative based on differences in cell wall
structure.
What is the difference between a selective and a differential test?
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