3. Now put a second red dot on the best fit line that is at exactly the double t

Question

3. Now put a second red dot on the best fit line that is at exactly the double the OD of the first dot. Record the number of cells must have doubled the time and OD for that second point. Since the OD double from the first to the second point, . Therefore, the time it took to go from the first OD reading to e second OD reading is the time it took for the culture to double. That is one generation time!!! Use the two pairs of numbers you have marked to calculate the generation time for the culture you grew. (Different cultures may give different generation times.) OD at 1" red dot OD at 2nd red dot232 Generation time 56 mioute Time at 1t red dot 15minues Time 2nd at red dot miautes 3. If you are told that a culture has an OD reading of 0.03 when there are one million cells per ml, how many cells per ml are present when the OD reads 0.015? 4. For the culture in question 3, what should you expect to get as an OD reading on a sample with six million cells/ml? 5. If you test a sample and find out that one million cells/ml of Escherichia coli has an OD reading of 0.23, would you expect the same OD, a higher or a lower OD if you had one million fungal cells? Explain your answer.

Explanation / Answer

3- As the OD of the culture is double the cell number also doubles.

So number of cells in 0.015 OD will be 0.5 million

4- 0.3 OD represents 1 million cells

So 0.6 OD will represent 2 million cells

1.2 OD will have 4 million cells

2.4 OD will have 8 million cells.

So for 6 million cells, OD should be around 2

5-

normally 1 OD of E-coli cells are around 2*108 cells

I OD of yeast cells are around 2*107 cells

So for One million of Yeast cells, there will be higher OD than Ecoli's one million cells, as the number of cells in yeast is less as compared to E-coli

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