Lab+3-+Quantification+of+Cultured+Microorganisms PDF

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microbiology foundation...

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Lab 3 Quantification of Cultured Microorganisms

“BIO250L”

Student Name: Click here to enter text. Access Code (located on the lid of your lab kit): Click here to enter text. Uncountable “Experiment 1- Direct Counts Following Serial Dilution” “Table 1: Experiment 1 Growth Results” “Plate”

“Classification”

“CFU/plate”

“10-1”

TNTC

Uncountable

“10-2”

CFU

4

“10-3”

TFTC

Uncountable

“10-4”

TFTC

Uncountable

“10-5”

TFTC

Uncountable

“10-6”

TFTC

Uncountable

“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?” Since you are introducing additional bacteria to the plate, I assume the population of the original sample would be TNTC if I infected an agar plate with 1mL of the original sample. “2. Did all the bacterial colonies on the countable plate(s) have a similar appearance? If not, how would you explain this?” The bacterial colonies on the countable plate did not appear to be identical, which might be due to the diluted sample, the transfer, or probable air contamination. “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?” 73 x 10^4 / 0.1 mL = 7,300,000 CFU/mL “4. List at least one advantage and one disadvantage to the direct plate counting method following serial dilution for determining bacterial concentration.” Direct plate counting after serial dilution has the benefit of limiting the number of cells transferred to a manageable quantity for counting. One disadvantage is that you will only have a few viable plates to deal with at the conclusion of the experiment. “5. Compare and contrast direct plate counts for bacterial and viral populations.”

Lab 3 Quantification of Cultured Microorganisms

“BIO250L”

Bacterial and viral populations are microorganisms that can be easily transmitted using the same transmission mechanisms. The difference between direct plate counts for bacterial and viral populations is that bacteria will form colonies on an agar plate, but viruses will not. “6. What are some sources of error in the serial dilution/direct plate counting method?” Errors in transferring samples, mixing the serial dilution improperly, or the environment not being at the right temperature for bacterial growth can all be sources of error in the serial dilution/direct plate counting technique. “Insert photo of your cultures after incubation with your name clearly visible in the background:”...