PORTAGE MICROBIOLOGY EXAM #5 CORRECT
QUESTIONS AND VERIFIED ANSWERS
Define the concept of universal precautions. - correct 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. - correct 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? - correct 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? -
correct 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? - correct 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: - correct 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. - correct 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 - correct 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.
QUESTIONS AND VERIFIED ANSWERS
Define the concept of universal precautions. - correct 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. - correct 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? - correct 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? -
correct 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? - correct 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: - correct 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. - correct 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 - correct 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.
