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Lab 11 Quiz
| Question | Answer |
|---|---|
| What is the purpose of creating serial dilutions? | Reduces number of cells to make it easier to estimate number of cells in a liquid sample |
| f you create 4 tubes of 1/10 dilutions, what will be the dilution factor for the tube #1? | 1/10 |
| If you create 4 tubes 1/10 dilutions, what will be the dilution factor for the tube #2? | 1/100 |
| If you create 4 tubes 1/10 dilutions, what will be the dilution factor for the tube #3? | 1/1000 |
| If you create 4 tubes 1/10 dilutions, what will be the dilution factor for the tube #4? | 1/10,000 |
| What would be the cells in each dilution if the original sample contained 500,000 cells/ mL in #1 tube? | 50,000 cells/ mL |
| What would be the cells in each dilution if the original sample contained 500,000 cells/ mL in #2 tube? | 5,000 cells/ mL |
| What would be the cells in each dilution if the original sample contained 500,000 cells/ mL in #3 tube? | 500 cells/ mL |
| What would be the cells in each dilution if the original sample contained 500,00 cells/ mL in #4 tube? | 50 cells/ mL |
| What is a CFU? | Colony forming unit |
| When counting colonies on serial dilution plates, why do we NOT want to select a plate with less than 30 colonies? | Less than 30 colonies is not statistically reliable. A differenc in one or two colonies can make a huge difference in the estimation of the cell count |
| What does TFTC mean? | Too few to count |
| When counting colonies on serial dilution plates, why do we NOT want to select a plate with more than 300 colonies? | More than 300 colonies is likely to lead to counting errors and colonies are more likely to start overlapping |
| What does TNTC? | Too numerous to count |
| What is the formula to estimate the number of CFUs? | Number of CFUs counted = number of CFUs per mL (dilution factor x volume plated) |
| How many CFUS are in your original culture if you counted 150 colonies on a plate where 0.1 mL of a 1/ 10,000 dilution was plated? | 150 150 TOTAL: 15,000,000 (1/10,000 x 0.1) = 0.00001 = |
| How many CFUS are in your original culture if you counted 62 colonies on a plate where 0.1 mL of a 1/1,000 dilution was plated? | 62 62 TOTAL: 620,000 (1/1,000 x 0.1) = 0.0001 |
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