Portage Microbiology BIOD171 Exam 5
Questions With Verified Answers.
Define the concept of universal precautions. - answer✔Universal precautions means any and all
samples, whether known or unknown, are to be treated as potentially hazardous (or pathogenic)
materials.
List at least 3 observations a researcher would be sure to note while assessing an unknown
microbial sample. - answer✔A lab researcher would be certain to note:
Size and shape
Any observable motility
Gram status (positive or negative)
The presence of any chemical reactions
Changes in color localized to the organism or the surrounding media
Capture (or draw) images of any of the characteristics described above
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 is catalse negative which means it cannot break down peroxides and if
any peroxides are present it would die.
Streptococcus is most often streaked onto: - answer✔Blood agar
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: (select all that apply)
Catalase activity
Hemolytic activity
Carbohydrate composition of antigens
All of the above - answer✔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.
Left untreated, strep throat can progress to ______ , which displays _____ hemolytic activity. -
answer✔Rheumatic fever; beta
True or False. Under most circumstances, staphylococcus can be found in ~30% of human
population where it remains pathogenic. - answer✔false; While staphylococcus can be found in
~30% of the human population, it remains non-symptomatic.
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