MCB2010CLab5Report

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Tallahassee Community College *

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2010

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Biology

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Feb 20, 2024

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docx

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3

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Name(s) : Nicole Linebaugh Section: 2360 Lec/Lab LAB 5 REPORT : Preparing a Standard Plate Count of Viable Bacteria 1. Record the data from your plate observation to the table below: Dilution Factor Number of colonies/plate 10 6 TFTC 10 7 TFTC 10 8 TFTC 10 9 TFTC 2. Calculate the selected plate for counting (CFU/ml). 0/10^-6= 0*10^6=0 CFU/ml. 3. Which plate did you select to calculate the CFU/ml? Why this plate was selected? I had selected the 10^6 plate, but any of the other plates would have been the same since all my plates had too few to count colonies. Generally, I would select a plate if I had a number of colonies/plates between 30 and 300 and use the dilution factor that is closer to 300 for more accuracy with +/- 10% error. 4. If you were to do a total count on this sample (as opposed to a viable count), would the total count most likely to be higher or lower than the viable count? Why? The total count most likely would be higher than the viable count because the total count would consider all the cells on the plate not just the living cells as it would in the viable count. 5. Why is it often necessary to dilute a sample before spreading it on a plate for a plate count? It is often necessary to dilute a sample before spreading it on a plate for a plate count because you need to count the colonies individually; when the plate is well concentrated, it is difficult to count and have congruent growth. 6. What is the main reason to prepare a serial dilution when performing a standard/viable plate count? The main reason to prepare a serial dilution when performing a standard/viable plate count is that the amount of concentration of the cells in the plate is to produce discrete colonies that can be countable for individual microbial growth in the 30-300 Colony range and identify the bacterium. 7. Why is it important to spread the culture liquid around on the surface of the agar when inoculating plates for a viable count? If the culture liquid is not spread, what will you see from the plate after incubation? This is important because spreading the culture liquid around on the surface of the agar will give the sample a larger area for cells to grow and lead to a better and more accurate count. If the culture liquid is not spread, you will see clumps.
8. Attach two labeled digital images of your plates which have most and least numbers of colonies. S. marcescens 10^-7 (Figure 1) S. marcescens 10^-9 (Figure 2)
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