Portage Microbiology BIOD171 Exam 4
1. True or False: Differential media is best suited for distinguishing between two
similar species of bacteria: True
Growth media does not contain restrictive factors, while selective media is best used to encourage the growth of one microbe
while simultaneously discouraging the growth of the other. Since two similar species of microbes are being studied they must
be ditterentiated under similar but just slightly ditterent conditions (ditterential media).
2. 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?:
Ditterential media
3. What are the requirements of a fastidious microbe?: A fastidious microbe is an organism with
complex growth requirements such that if absent it will not grow. Enriched medias thus contain these specific and essential
nutrients required for the growth of a particular subset of microorganisms.
4. True or False: LB agar is classified as a selective, non-differential media.: False.
5. The polysaccharide-based hardening agent added to LB media to produce LB
agar is derived from what?: Seaweed (algae) extract.
6. Blood agar is which type of medium? Select all that apply.
1/8
, Selective Enriched
Selective and Differential
Differential: Enriched Ditterential
7. Match the following hemolytic class with its description of activity.
1. Alpha hemolysis A. No change.
2. Beta hemolysis B. Greenish-brown color
3. Gamma hemolysis C. Distinct zone of clearing: 1. Alpha hemolysis --> B. Greenish-brown color
2. Beta hemolysis ---> C. Distinct zone of clearing
3. Gamma hemolysis --> A. No change.
2/8
1. True or False: Differential media is best suited for distinguishing between two
similar species of bacteria: True
Growth media does not contain restrictive factors, while selective media is best used to encourage the growth of one microbe
while simultaneously discouraging the growth of the other. Since two similar species of microbes are being studied they must
be ditterentiated under similar but just slightly ditterent conditions (ditterential media).
2. 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?:
Ditterential media
3. What are the requirements of a fastidious microbe?: A fastidious microbe is an organism with
complex growth requirements such that if absent it will not grow. Enriched medias thus contain these specific and essential
nutrients required for the growth of a particular subset of microorganisms.
4. True or False: LB agar is classified as a selective, non-differential media.: False.
5. The polysaccharide-based hardening agent added to LB media to produce LB
agar is derived from what?: Seaweed (algae) extract.
6. Blood agar is which type of medium? Select all that apply.
1/8
, Selective Enriched
Selective and Differential
Differential: Enriched Ditterential
7. Match the following hemolytic class with its description of activity.
1. Alpha hemolysis A. No change.
2. Beta hemolysis B. Greenish-brown color
3. Gamma hemolysis C. Distinct zone of clearing: 1. Alpha hemolysis --> B. Greenish-brown color
2. Beta hemolysis ---> C. Distinct zone of clearing
3. Gamma hemolysis --> A. No change.
2/8
