Portage Microbiology BIOD171 Exam 5
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? - ✔✔✔✔✔ 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? -
✔✔✔✔✔ 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? - ✔✔✔✔✔ 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: - ✔✔✔✔✔ 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. - ✔✔✔✔✔ 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 - ✔✔✔✔✔ 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. - ✔✔✔✔✔ Rheumatic fever; beta
True or False. Under most circumstances, staphylococcus can be found in ~30% of
human population where it remains pathogenic. - ✔✔✔✔✔ false; While
staphylococcus can be found in ~30% of the human population, it remains non-
symptomatic.
When a bacterium neither harms nor benefits from the host from which it obtains
nutrients, it is referred to as being ___________. - ✔✔✔✔✔ Commensal
Attachment - ✔✔✔✔✔ pathogen finds a specific target tissue and adhere
evasion - ✔✔✔✔✔ pathogen masks its own antigens to hide from the host's immune
system
entry - ✔✔✔✔✔ utilization of a portal to gain access to host's tissues
Match the following diseases with their respective symptoms:
1. folliculitis
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? - ✔✔✔✔✔ 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? -
✔✔✔✔✔ 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? - ✔✔✔✔✔ 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: - ✔✔✔✔✔ 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. - ✔✔✔✔✔ 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 - ✔✔✔✔✔ 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. - ✔✔✔✔✔ Rheumatic fever; beta
True or False. Under most circumstances, staphylococcus can be found in ~30% of
human population where it remains pathogenic. - ✔✔✔✔✔ false; While
staphylococcus can be found in ~30% of the human population, it remains non-
symptomatic.
When a bacterium neither harms nor benefits from the host from which it obtains
nutrients, it is referred to as being ___________. - ✔✔✔✔✔ Commensal
Attachment - ✔✔✔✔✔ pathogen finds a specific target tissue and adhere
evasion - ✔✔✔✔✔ pathogen masks its own antigens to hide from the host's immune
system
entry - ✔✔✔✔✔ utilization of a portal to gain access to host's tissues
Match the following diseases with their respective symptoms:
1. folliculitis
