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BIOL271/ BIOL 271 Module 4 Microbiology | Updated
2026/2027 Study Questions with Verified Answers |
Portage Learning | Grade A Review
True or False: Growth media is best suited for distinguishing between two similar species of
bacteria
False. Growth media is designed to simply support (and not restrict) microbial growth
A researcher is asked to determine which of two vials contains e coli and which contains
salmonella. Knowing both gram-negative while only one of them is capable of fermenting
lactose, which type of media would be best suited (multiple choice)
Differential media distinguishes between two, often related, microbes
What are the requirements of a fastidious microbe? (short answer)
A fastidious microbe is an organism with complex growth requirements such that is absent it will
not grow. Enriched medias thus contain these specific and essential nutrients required for the
growth of a particular subset of microorganisms.
True or False: LB agar is classified as a selective, non-differential media
False
What is agar used for in microbiology? (short answer)
Agar is used to create a solid, smooth surface on which microbes can grow
Alpha hemolysis (matching)
Incomplete hemolytic activity
Beta hemolysis (matching)
Complete hemolytic activity
Gamma hemolysis (matching)
No hemolytic activity
Colombia CNA agar is most closely related to which media (multiple choice)
CNA agar is similar to VAP as it is also enriched with blood and allows for differentiation based
on hemolytic patterns
True or False: Chocolate agar gets its brown color from cocoa to produce an enriched media
False
, A researcher is studying a strain of e coli currently growing on a MacConkey plate. However, the
researcher can't remember if e coli is gram positive or gram negative. Would a gram stain be
necessary to confirm? Why or why not? (short answer)
No. A gram stain would not be necessary, as only gram negative microbes will grown on
MacConkey agar. Thus, e coli is a gram negative microbe
In an attempt to detect the presence of the pathogenic strain of e coli O157:H7, a researcher
spread culture onto a MacConkey agar with failed results. What type of agar should they
(correctly) try next? Why? (short answer)
The microbe should be plated on SMAC as it is specifically formulated to detect O157:H7.
Pathogenic e coli cannot ferment sorbitol while non-pathogenic e coli can ferment both sorbitol
and lactose. Therefore, colonies that ferment can be differentiated from non-fermenters.
What is the gram status of microbes growing on eosin methylene blue agar plates? (short answer)
Gram-negative
What is the process of spreading a bacterial culture onto a petri dish? (short answer)
Plating
Mannitol salt agar will turn what color in the presence of the pathogenic strain staphylococcus
aureus? (short answer)
Yellow
In order to visual individual colonies of bacteria, would you culture your sample in a liquid
media or on a solid (agar) media? Why? (short answer)
Solid media. The primary advantage is that cells are held into place. When grown in a nutrient
broth, bacterial cells can multiply but are free to move around in solution. When grown on agar
within a petri dish the fixed in such a way as to form colonies
True or False: the visualization of colonies on a petri dish represents bacterial cells that have
often multiplied a million times over
True
True or False: the purpose of a quadrant streak expand a bacterial population
False
To be considered a pure culture, the sample can be traced back to a single cell and _________
The culture must also be free from external contaminants. Would not contain multiple bacterial
species
When performing a quadrants streak, the sample is spread across the plate in such as way as to
form what? (short answer)
A dilution gradient is formed. The resulting gradient should always contain within it the growth
BIOL271/ BIOL 271 Module 4 Microbiology | Updated
2026/2027 Study Questions with Verified Answers |
Portage Learning | Grade A Review
True or False: Growth media is best suited for distinguishing between two similar species of
bacteria
False. Growth media is designed to simply support (and not restrict) microbial growth
A researcher is asked to determine which of two vials contains e coli and which contains
salmonella. Knowing both gram-negative while only one of them is capable of fermenting
lactose, which type of media would be best suited (multiple choice)
Differential media distinguishes between two, often related, microbes
What are the requirements of a fastidious microbe? (short answer)
A fastidious microbe is an organism with complex growth requirements such that is absent it will
not grow. Enriched medias thus contain these specific and essential nutrients required for the
growth of a particular subset of microorganisms.
True or False: LB agar is classified as a selective, non-differential media
False
What is agar used for in microbiology? (short answer)
Agar is used to create a solid, smooth surface on which microbes can grow
Alpha hemolysis (matching)
Incomplete hemolytic activity
Beta hemolysis (matching)
Complete hemolytic activity
Gamma hemolysis (matching)
No hemolytic activity
Colombia CNA agar is most closely related to which media (multiple choice)
CNA agar is similar to VAP as it is also enriched with blood and allows for differentiation based
on hemolytic patterns
True or False: Chocolate agar gets its brown color from cocoa to produce an enriched media
False
, A researcher is studying a strain of e coli currently growing on a MacConkey plate. However, the
researcher can't remember if e coli is gram positive or gram negative. Would a gram stain be
necessary to confirm? Why or why not? (short answer)
No. A gram stain would not be necessary, as only gram negative microbes will grown on
MacConkey agar. Thus, e coli is a gram negative microbe
In an attempt to detect the presence of the pathogenic strain of e coli O157:H7, a researcher
spread culture onto a MacConkey agar with failed results. What type of agar should they
(correctly) try next? Why? (short answer)
The microbe should be plated on SMAC as it is specifically formulated to detect O157:H7.
Pathogenic e coli cannot ferment sorbitol while non-pathogenic e coli can ferment both sorbitol
and lactose. Therefore, colonies that ferment can be differentiated from non-fermenters.
What is the gram status of microbes growing on eosin methylene blue agar plates? (short answer)
Gram-negative
What is the process of spreading a bacterial culture onto a petri dish? (short answer)
Plating
Mannitol salt agar will turn what color in the presence of the pathogenic strain staphylococcus
aureus? (short answer)
Yellow
In order to visual individual colonies of bacteria, would you culture your sample in a liquid
media or on a solid (agar) media? Why? (short answer)
Solid media. The primary advantage is that cells are held into place. When grown in a nutrient
broth, bacterial cells can multiply but are free to move around in solution. When grown on agar
within a petri dish the fixed in such a way as to form colonies
True or False: the visualization of colonies on a petri dish represents bacterial cells that have
often multiplied a million times over
True
True or False: the purpose of a quadrant streak expand a bacterial population
False
To be considered a pure culture, the sample can be traced back to a single cell and _________
The culture must also be free from external contaminants. Would not contain multiple bacterial
species
When performing a quadrants streak, the sample is spread across the plate in such as way as to
form what? (short answer)
A dilution gradient is formed. The resulting gradient should always contain within it the growth
