MCB 2010C MICROBIOLOGY FINAL EXAM
LATEST 2025 FALL-SPRING FSW GRADED A+
Name: Antonnette Burgos
Answer the questions below:
1. The first 2-3 plates from the video were not be selected for a viable count and calculation because: (2.5
points) a. They did not contain bacterial growth
b. They were not plated correctly
c. They were contaminated
d. They were confluent and not allow to obtain 30-300 colonies CORR ANS: D
2. The ultimate purpose of performing a serial dilution, plating the diluted bacterial samples on agar plates,
and counting the viable colonies from the plate which contained 30-300 colonies is: (2.5 points) a. To find out
the original concentration of the bacterial sample used for testing
b. To make the plates easy to count
c. To allow bacterial cells to grow their best
d. To know the morphology of the bacterial cells used for testing CORR ANS: A
3. When 0.1 ml of the same dilution 10-4 is plated, the final plate dilution is: (2.5 points)
a. 10-5
b. 10+5
c. 10-3
d. 10+3
CORR ANS: A
4. ________________ may be counted by diluting samples, plating the dilutions on solid medium, and
counting the colonies that arise. (2.5 points) a. Total count
b. Plate count
c. Viable bacteria
d. All of the above CORR ANS: D
5. You have collected 4 plates after adequate incubation as shown below:
10-6: 465 colonies, 10-7: 280 colonies, 10-8: 20 colonies, and 10-9: no growth. Please CORR ANS the
questions: a) Which plate did you select to calculate the CFU/ml? Why this plate was selected?
10-7; I chose this plate because it contained between 30 and 300 colonies so it will yield a more
reliable/accurate count
b) Calculate the selected plate for counting (CFU/ml)
LATEST 2025 FALL-SPRING FSW GRADED A+
Name: Antonnette Burgos
Answer the questions below:
1. The first 2-3 plates from the video were not be selected for a viable count and calculation because: (2.5
points) a. They did not contain bacterial growth
b. They were not plated correctly
c. They were contaminated
d. They were confluent and not allow to obtain 30-300 colonies CORR ANS: D
2. The ultimate purpose of performing a serial dilution, plating the diluted bacterial samples on agar plates,
and counting the viable colonies from the plate which contained 30-300 colonies is: (2.5 points) a. To find out
the original concentration of the bacterial sample used for testing
b. To make the plates easy to count
c. To allow bacterial cells to grow their best
d. To know the morphology of the bacterial cells used for testing CORR ANS: A
3. When 0.1 ml of the same dilution 10-4 is plated, the final plate dilution is: (2.5 points)
a. 10-5
b. 10+5
c. 10-3
d. 10+3
CORR ANS: A
4. ________________ may be counted by diluting samples, plating the dilutions on solid medium, and
counting the colonies that arise. (2.5 points) a. Total count
b. Plate count
c. Viable bacteria
d. All of the above CORR ANS: D
5. You have collected 4 plates after adequate incubation as shown below:
10-6: 465 colonies, 10-7: 280 colonies, 10-8: 20 colonies, and 10-9: no growth. Please CORR ANS the
questions: a) Which plate did you select to calculate the CFU/ml? Why this plate was selected?
10-7; I chose this plate because it contained between 30 and 300 colonies so it will yield a more
reliable/accurate count
b) Calculate the selected plate for counting (CFU/ml)
