BIO 171 MODULE 5 QUESTIONS AND
ANSWERS WITH COMPLETE
SOLUTIONS 100% CORRECT RATED
A+||LATEST UPDATED 2025
Universal Precautions
✔✔The practice of treating all biological samples—regardless of origin—as if they
may contain hazardous or pathogenic organisms, to ensure safety and prevent
contamination.
Observations a researcher would be sure to note while assessing an unknown
microbial sample include:
✔✔1. Size and shape of the organism
✔✔2. Any visible motility (movement)
✔✔3. Gram stain result (positive or negative)
✔✔4. Presence of chemical reactions (e.g., bubbling, precipitates)
✔✔5. Color changes, either in the organism or the surrounding medium
✔✔6. Documentation through images or drawings of the observed features
While observing an unknown sample of limited amounts, a researcher must
determine the following observations: (1) the presence of any motility and (2) its
Gram status using the same sample—the liquid sample cannot be divided. Which
would you determine first and why? - ANSWER✔✔You must determine motility
before determining the Gram status. Motility requires a wet mount, while Gram
staining requires heat fixing the sample. If one were to begin with the Gram stain
the heat fixation process would kill the organism, making any observations
regarding motility impossible. The correct approach would be to place the liquid
culture on a glass slide and determine its motility status. Next, the same liquid
culture can be heat fixed and Gram stained.
, A facultative anaerobe is a microorganism capable of growth under what
conditions? - ANSWER✔✔A facultative anaerobe is capable of growth under
aerobic (with oxygen) and anaerobic (without oxygen) conditions.
As Streptococcus is catalase negative would it thrive or die in the presence of
peroxides? Why? - ANSWER✔✔Streptococcus would not survive in the presence
of peroxides—it is unable to breakdown peroxides (catalase negative). Left
unchecked, peroxides would damage the cellular integrity of Strep causing
lysis/cell death.
Streptococcus is most often streaked onto what type of agar? - ANSWER✔✔Strep
is often cultured on Blood agar plates to determine its hemolytic properties, which
aids in the classification (and differentiation) process.
True or False. The Lancefield groups are used to subdivide antigenic groups of
gamma-hemolytic Streptococcus. - ANSWER✔✔FALSE. The Lancefield
groupings are used to subdivide beta-hemolytic Strep.
The distinctions for Lancefield subgroupings lie in its:
A.) Hemolytic activity
B.) Catalase activity
C.) Carbohydrate composition of antigens
D.) All of the above - ANSWER✔✔C.)Carbohydrate composition of antigens
Carbohydrate composition of antigens present in the cell wall determines the
Lancefield groupings (A, B, C, etc). Note, ALL strep under Lancefield groupings
are (by definition) catalase negative and beta-hemolytic. Thus, answers A and C
cannot be used to subdivide streptococcal species.
ANSWERS WITH COMPLETE
SOLUTIONS 100% CORRECT RATED
A+||LATEST UPDATED 2025
Universal Precautions
✔✔The practice of treating all biological samples—regardless of origin—as if they
may contain hazardous or pathogenic organisms, to ensure safety and prevent
contamination.
Observations a researcher would be sure to note while assessing an unknown
microbial sample include:
✔✔1. Size and shape of the organism
✔✔2. Any visible motility (movement)
✔✔3. Gram stain result (positive or negative)
✔✔4. Presence of chemical reactions (e.g., bubbling, precipitates)
✔✔5. Color changes, either in the organism or the surrounding medium
✔✔6. Documentation through images or drawings of the observed features
While observing an unknown sample of limited amounts, a researcher must
determine the following observations: (1) the presence of any motility and (2) its
Gram status using the same sample—the liquid sample cannot be divided. Which
would you determine first and why? - ANSWER✔✔You must determine motility
before determining the Gram status. Motility requires a wet mount, while Gram
staining requires heat fixing the sample. If one were to begin with the Gram stain
the heat fixation process would kill the organism, making any observations
regarding motility impossible. The correct approach would be to place the liquid
culture on a glass slide and determine its motility status. Next, the same liquid
culture can be heat fixed and Gram stained.
, A facultative anaerobe is a microorganism capable of growth under what
conditions? - ANSWER✔✔A facultative anaerobe is capable of growth under
aerobic (with oxygen) and anaerobic (without oxygen) conditions.
As Streptococcus is catalase negative would it thrive or die in the presence of
peroxides? Why? - ANSWER✔✔Streptococcus would not survive in the presence
of peroxides—it is unable to breakdown peroxides (catalase negative). Left
unchecked, peroxides would damage the cellular integrity of Strep causing
lysis/cell death.
Streptococcus is most often streaked onto what type of agar? - ANSWER✔✔Strep
is often cultured on Blood agar plates to determine its hemolytic properties, which
aids in the classification (and differentiation) process.
True or False. The Lancefield groups are used to subdivide antigenic groups of
gamma-hemolytic Streptococcus. - ANSWER✔✔FALSE. The Lancefield
groupings are used to subdivide beta-hemolytic Strep.
The distinctions for Lancefield subgroupings lie in its:
A.) Hemolytic activity
B.) Catalase activity
C.) Carbohydrate composition of antigens
D.) All of the above - ANSWER✔✔C.)Carbohydrate composition of antigens
Carbohydrate composition of antigens present in the cell wall determines the
Lancefield groupings (A, B, C, etc). Note, ALL strep under Lancefield groupings
are (by definition) catalase negative and beta-hemolytic. Thus, answers A and C
cannot be used to subdivide streptococcal species.
