BIOL 402 Exam 3 || Certified Answers 100%.
The API-20E system is a set of biochemical tests designed for the identification of certain types
of bacteria... What did the "E" stand for? correct answers enterobacteriaceae
From our laboratory manual, regarding the mannitol salt agar test: With the diversity of
microorganisms in the world, how can a single test such as MSA be used to "confidently"
identify Staphylococcus aureus? correct answers Using this test alone, one cannot "confidently"
identify S. aureus. Other species can grow at 7.5% NaCl and ferment mannitol - these would
appear identical.
Growth of an organism on Mannitol Salt Agar plates demonstrates that the organism correct
answers tolerates 7.5% salt concentration
Which of the following would be most likely to cause false negatives on a diagnostic test?
correct answers low test sensitivity
From our laboratory manual, regarding the catalase test: Would a false positive from the reaction
between the inoculating loop and hydrogen peroxide be caused by poor specificity or poor
sensitivity of the test system? correct answers poor specificity
Suppose you have inoculated 100 μL of a sample diluted by a factor of 10-2 on a nutrient agar
plate. After incubation, you count 22 colonies. What was the original cell density (in CFU/mL)?
correct answers 22,000
Which of the following contained the antibodies that bound to microbes during the agglutination
test? correct answers the agglutination reagents
From our laboratory manual, regarding the DNA hydrolysis test: Suggest a reason why this test
is read after only 24 hours while other tests (e.g., gelatinase test) may take a week. What would
be the likely consequences of incubating DNase Agar for a week? correct answers DNases would
diffuse across the entire plate, "clearing" the media around even DNase-negative samples
Which of the following would be most likely to cause false positives on a diagnostic test? correct
answers low test specificity
In a positive PYR test, an enzyme catalyzes conversion of substrate to product; then a chemical
reaction is used to convert the initial (colorless) product to a secondary (visibly colored)
product ... Where did the enzyme originate (come from)? correct answers the bacteria
A "hot pink" (or bright-reddish) result in the PYR test indicates correct answers the organism is
positive for L-pyrrolidonyl arylamidase
Historically, some bacterial species were grown in candle jars, in which a candle is placed in the
jar, lit, and the lid closed to extinguish the flame (During the mixed-double-unknown project, we
incubated our blood agar plates in a similar high-[CO2] environment using the plastic jars)...
, Which of the following types of bacteria would *NOT* grow in "candle-jar" type environments?
correct answers obligate anaerobes
Ultraviolet radiation interacts with the DNA, causing pyrimidine dimers. How does this (dimer
formation) impact function of the cell? correct answers interferes with DNA replication and
transcription
If cells contain enzymes to repair DNA damage, how/why can UV radiation be lethal? correct
answers the enzymes take time to act and can only repair small amounts of damage
From our laboratory manual, regarding UV radiation & Repair (Ex. 10-5): "What does the
relatively heavy growth on the plates covered by the masks and the lid during exposure tell you
about UV radiation? correct answers short-wavelength light does not penetrate well - only
effective on surfaces
From our laboratory manual, regarding the pGlo transformation: "Why were the vials [of
transformed cells] incubated for 10 min in LB broth rather than transferring their contents
directly to the plates? correct answers to allow the ampicillin-resistance protein to be produced
In a successful pGlo transformation experiment, the trait which allowed the cells to grow on LB
+ ampicillin and LB + ampicillin + arabinose was the acquisition of: correct answers ampicillin
resistance
In a typical pGlo transformation procedure, approximately what percentage of bacteria take up
the plasmid? (That is, what percentage of cells that undergo heat shock treatment end up
"transformed"?) correct answers very few <0.1%
From our laboratory manual, regarding the pGlo transformation: Why does the
LB/amp/ara/+DNA plate fluoresce when the LB/amp/+DNA plate does not? correct answers
because the GFP is only expressed in presence of arabinose
From our laboratory manual, regarding the Blood agar (hemolysis) test: The streak-stab
technique, used to promote streptolysin activity, is preferred over incubating the plates
anaerobically. Why? correct answers some hemolytic enzymes are destroyed by high levels of
oxygen, but the cultures are not anaerobes
In the Kirby-Bauer antibiotic disk sensitivity testing procedure (described & used in exercise 7-
3), which of the following processes creates a gradient of antibiotic concentration? correct
answers passive *diffusion* (random movement of substances through semi-solid media)
In the Kirby-Bauer antibiotic disk sensitivity testing procedure, what (approximately) does the
drug concentration at the edge of the zone of inhibition correspond to? correct answers minimum
inhibitory concentration
The API-20E system is a set of biochemical tests designed for the identification of certain types
of bacteria... What did the "E" stand for? correct answers enterobacteriaceae
From our laboratory manual, regarding the mannitol salt agar test: With the diversity of
microorganisms in the world, how can a single test such as MSA be used to "confidently"
identify Staphylococcus aureus? correct answers Using this test alone, one cannot "confidently"
identify S. aureus. Other species can grow at 7.5% NaCl and ferment mannitol - these would
appear identical.
Growth of an organism on Mannitol Salt Agar plates demonstrates that the organism correct
answers tolerates 7.5% salt concentration
Which of the following would be most likely to cause false negatives on a diagnostic test?
correct answers low test sensitivity
From our laboratory manual, regarding the catalase test: Would a false positive from the reaction
between the inoculating loop and hydrogen peroxide be caused by poor specificity or poor
sensitivity of the test system? correct answers poor specificity
Suppose you have inoculated 100 μL of a sample diluted by a factor of 10-2 on a nutrient agar
plate. After incubation, you count 22 colonies. What was the original cell density (in CFU/mL)?
correct answers 22,000
Which of the following contained the antibodies that bound to microbes during the agglutination
test? correct answers the agglutination reagents
From our laboratory manual, regarding the DNA hydrolysis test: Suggest a reason why this test
is read after only 24 hours while other tests (e.g., gelatinase test) may take a week. What would
be the likely consequences of incubating DNase Agar for a week? correct answers DNases would
diffuse across the entire plate, "clearing" the media around even DNase-negative samples
Which of the following would be most likely to cause false positives on a diagnostic test? correct
answers low test specificity
In a positive PYR test, an enzyme catalyzes conversion of substrate to product; then a chemical
reaction is used to convert the initial (colorless) product to a secondary (visibly colored)
product ... Where did the enzyme originate (come from)? correct answers the bacteria
A "hot pink" (or bright-reddish) result in the PYR test indicates correct answers the organism is
positive for L-pyrrolidonyl arylamidase
Historically, some bacterial species were grown in candle jars, in which a candle is placed in the
jar, lit, and the lid closed to extinguish the flame (During the mixed-double-unknown project, we
incubated our blood agar plates in a similar high-[CO2] environment using the plastic jars)...
, Which of the following types of bacteria would *NOT* grow in "candle-jar" type environments?
correct answers obligate anaerobes
Ultraviolet radiation interacts with the DNA, causing pyrimidine dimers. How does this (dimer
formation) impact function of the cell? correct answers interferes with DNA replication and
transcription
If cells contain enzymes to repair DNA damage, how/why can UV radiation be lethal? correct
answers the enzymes take time to act and can only repair small amounts of damage
From our laboratory manual, regarding UV radiation & Repair (Ex. 10-5): "What does the
relatively heavy growth on the plates covered by the masks and the lid during exposure tell you
about UV radiation? correct answers short-wavelength light does not penetrate well - only
effective on surfaces
From our laboratory manual, regarding the pGlo transformation: "Why were the vials [of
transformed cells] incubated for 10 min in LB broth rather than transferring their contents
directly to the plates? correct answers to allow the ampicillin-resistance protein to be produced
In a successful pGlo transformation experiment, the trait which allowed the cells to grow on LB
+ ampicillin and LB + ampicillin + arabinose was the acquisition of: correct answers ampicillin
resistance
In a typical pGlo transformation procedure, approximately what percentage of bacteria take up
the plasmid? (That is, what percentage of cells that undergo heat shock treatment end up
"transformed"?) correct answers very few <0.1%
From our laboratory manual, regarding the pGlo transformation: Why does the
LB/amp/ara/+DNA plate fluoresce when the LB/amp/+DNA plate does not? correct answers
because the GFP is only expressed in presence of arabinose
From our laboratory manual, regarding the Blood agar (hemolysis) test: The streak-stab
technique, used to promote streptolysin activity, is preferred over incubating the plates
anaerobically. Why? correct answers some hemolytic enzymes are destroyed by high levels of
oxygen, but the cultures are not anaerobes
In the Kirby-Bauer antibiotic disk sensitivity testing procedure (described & used in exercise 7-
3), which of the following processes creates a gradient of antibiotic concentration? correct
answers passive *diffusion* (random movement of substances through semi-solid media)
In the Kirby-Bauer antibiotic disk sensitivity testing procedure, what (approximately) does the
drug concentration at the edge of the zone of inhibition correspond to? correct answers minimum
inhibitory concentration
