Standard Plate Count Worksheet
This worksheet covers the principles and procedures of the Standard Plate Count method, including serial dilutions and colony counting.
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Standards
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Standard Plate Count Worksheet
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Read each question carefully and answer to the best of your ability. Show all calculations where required.
1. What is the primary purpose of performing a Standard Plate Count?
To identify specific types of bacteria.
To estimate the number of viable bacterial cells in a sample.
To measure the size of bacterial colonies.
To sterilize bacterial samples.
2. Why are serial dilutions performed before plating a bacterial sample?
To make the bacteria more visible.
To ensure a countable number of colonies on the agar plate.
To kill off unwanted bacteria.
To increase the growth rate of bacteria.
3. In a Standard Plate Count, bacterial colonies are counted on an agar plate after an incubation period, and each colony is assumed to have originated from a single .
4. The optimal range for counting colonies on a plate is typically between and colony-forming units (CFU).
5. Describe the process of making a 1:100 dilution from an undiluted bacterial sample.
6. A Standard Plate Count can differentiate between live and dead bacterial cells.
True
False
7. For accurate results, the plates should be incubated at a temperature that is optimal for the growth of the target bacteria.
True
False
8. A student performs a Standard Plate Count and obtains 150 colonies on a plate that was inoculated with 0.1 mL of a 10^-5 dilution. Calculate the original bacterial concentration (CFU/mL) in the undiluted sample.
9. Draw a diagram illustrating a Petri dish with approximately 75 colonies. Indicate how you would count them.
