BIOD 171: MODULE 4
T/F: 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 are Gram-negative while only one of them is capable of fermenting lactose, which type of
media would be best suited?
Differential media
What are the requirements of a fastidious microbe?
A fastidious microbe is an organism with complex growth requirements and will not grow without then.
Enriched medias thus contain these specific and essential nutrients required for the growth of a
particular subset of microorganisms.
T/F: LB agar is classified as a non-selective, non-differential media
True
The polysaccharide-based hardening agent added to LB media to produce LB agar is derived from what?
Seaweed extract
Blood agar is which type of medium? Select all that apply:
- Selective and Differential
- Enriched
- Differential
- Selective
- Enriched
- Differential
Match the following hemolytic class with its description of activity:
1. Alpha hemolysis
2. Beta hemolysis
3. Gamma hemolysis
A. No change
B. Greenish-brown color
C. Distinct zone of clearing
, 1. Alpha hemolysis- Greenish-brown color (B)
2. Beta hemolysis- Distinct zone of clearing (C)
3. Gamma hemolysis- No change (A)
Match the following hemolytic class with its description of activity:
1. Alpha hemolysis
2. Beta hemolysis
3. Gamma hemolysis
A. No hemolytic activity
B. Incomplete hemolytic activity
C. Complete hemolytic activity
1. Alpha hemolysis- Incomplete hemolytic activity (B)
2. Beta hemolysis- Complete hemolytic activity (C)
3. Gamma hemolysis- No hemolytic activity (A)
Columbia CNA agar is most closely related to which media:
Blood agar
CNA agar is similar to BAP as its also enriched with blood and allows for differentiation based on
hemolytic patterns
T/F: Chocolate agar gets its brown color from cocoa to produce an enriched media
False
chocolate is never added to the media. the name is derived simply based on the color that actually
comes from the presence of 'cooked' (lysed) red blood cells in the media
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?
No, because gram negative microbes only grow on macConkey agar
In an attempt to detect the presence of the pathogenic strain of E. coli O157:H7, a researcher spread a
culture onto a MacConkey agar with failed results. What type of agar should they (correctly) try next?
Why?
The SMAC should be tried next because it can be differentiated by lactose fermentation and sorbitol
fermentation, both of which can be fermented by the non-pathogenic strain
What is the Gram status (positive or negative) of microbes growing on Eosin Methylene Blue (EMB) agar
plates?
Gram-negative because gram positive bacteria growth is restricted by EMB plates
T/F: 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 are Gram-negative while only one of them is capable of fermenting lactose, which type of
media would be best suited?
Differential media
What are the requirements of a fastidious microbe?
A fastidious microbe is an organism with complex growth requirements and will not grow without then.
Enriched medias thus contain these specific and essential nutrients required for the growth of a
particular subset of microorganisms.
T/F: LB agar is classified as a non-selective, non-differential media
True
The polysaccharide-based hardening agent added to LB media to produce LB agar is derived from what?
Seaweed extract
Blood agar is which type of medium? Select all that apply:
- Selective and Differential
- Enriched
- Differential
- Selective
- Enriched
- Differential
Match the following hemolytic class with its description of activity:
1. Alpha hemolysis
2. Beta hemolysis
3. Gamma hemolysis
A. No change
B. Greenish-brown color
C. Distinct zone of clearing
, 1. Alpha hemolysis- Greenish-brown color (B)
2. Beta hemolysis- Distinct zone of clearing (C)
3. Gamma hemolysis- No change (A)
Match the following hemolytic class with its description of activity:
1. Alpha hemolysis
2. Beta hemolysis
3. Gamma hemolysis
A. No hemolytic activity
B. Incomplete hemolytic activity
C. Complete hemolytic activity
1. Alpha hemolysis- Incomplete hemolytic activity (B)
2. Beta hemolysis- Complete hemolytic activity (C)
3. Gamma hemolysis- No hemolytic activity (A)
Columbia CNA agar is most closely related to which media:
Blood agar
CNA agar is similar to BAP as its also enriched with blood and allows for differentiation based on
hemolytic patterns
T/F: Chocolate agar gets its brown color from cocoa to produce an enriched media
False
chocolate is never added to the media. the name is derived simply based on the color that actually
comes from the presence of 'cooked' (lysed) red blood cells in the media
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?
No, because gram negative microbes only grow on macConkey agar
In an attempt to detect the presence of the pathogenic strain of E. coli O157:H7, a researcher spread a
culture onto a MacConkey agar with failed results. What type of agar should they (correctly) try next?
Why?
The SMAC should be tried next because it can be differentiated by lactose fermentation and sorbitol
fermentation, both of which can be fermented by the non-pathogenic strain
What is the Gram status (positive or negative) of microbes growing on Eosin Methylene Blue (EMB) agar
plates?
Gram-negative because gram positive bacteria growth is restricted by EMB plates
