Question

1:23 h Date Laboratory Report 45) Determination of a Bacterial Growth Curve and the Generation Time of a Culture 1. Collect your data on alsorance in the following table. Inbeton Time Absorbance 600 m 083 336 SIE .769 971 150 2. Estimate the generation time for this E. coli culture by the indirect method using your growth curve graph and extrapolations from the absorbances for doubling. Be sure to put UNITS on your answers. * From growth curve (indicate what numbers you used as your doubling and the subtraction you did to get an estimated doubling time generation time.) b. Now, using the formula method, choose two actual data points from your table above (make sure they are in log phase) and calculate the doubling time/generation time. Show your work. 1 3. How do the numbers from question 2 compare? Which one do you think is more accurate and why? 4. In summary, what is the major purpose of this experiment? 319

Answer 1

ANSWER 2.A -

The estimated generation or the doubling time can be calculated from the following formula [Generation time = time required for obtaining the absorbance of 0.52 (0.518) - time required for obtaining the absorbance of 0.34 (0.336)]

This time period for absorbance marks the doubling of the bacterial cells which remain same for all the points mentioned in the graph. In this case, the doubling time is calculated to be 30 minutes.

Generation time / Doubling time = (60 minutes) - (30 minutes)

= 30 minutes

ANSWER 2.B -

Generation (formula method) = (T2 - T1) x Log(2) / Log(absorbance in terms of OD at 60 min) - Log(absorbance in terms of OD at 30 min)

= (60-30) x (0.3010) / Log(0.518) - log(0.336)

= (30) x (0.3010) / (-0.2856) - (-0.4736)

= (9.03) / (-0.2856) + (0.4736)

= (9.03) / (0.188)

= 48.03 minutes

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