STRAIGHTERLINE BIO250L Lab 3 Quantification of Cultured Microorganisms 2022

Lab 3 Quantification of Cultured
Microorganisms “BIO250L”
Student Name
Access Code (located on the lid of your lab kit):


“Experiment 1- Direct Counts Following Serial Dilution”
“Table 1: Experiment 1 Growth Results”

“Plate” “Classification” “CFU/plate”


“10-1” TNTC 0.01

“10-2” TNTC 0.001

“10-3” TNTC 0.001

“10-4” TFTC 0.00001

“10-5” TFTC 0.000001

“10-6” TFTC 0.000001




“Post-Lab Questions”
“1. What was the population density of the original sample? What would have happened if you had
inoculated an agar plate with 1mL of the original sample?”
If the agar plate had 1mL of the original sample, the population density would increase a lot.
“2. Did all the bacterial colonies on the countable plate(s) have a similar appearance? If not, how would
you explain this?”
They were all similar in some ways but not identical because of the different dilution strengths. I’ve also
realized the second I took the cover off, it started to smell really bad.
“3. You have performed a serial dilution of an unknown sample and counted 73 CFU on a countable
plate that was marked as a 10-4 dilution and you used 0.1mL to inoculate the plate. What is the
population density of the original sample?”
1.0 mL
“4. List at least one advantage and one disadvantage to the direct plate counting method following serial
dilution for determining bacterial concentration.”