Essay on Ecoli

597 Words3 Pages
Assignment 1 for MCB 3020L Spring 2014 (due 2/24 or 2/26) Instructions: * Your answers have to be typed and double spaced. * Put the date, your name and your TA’s name on the cover page of this assignment. * “Give a detailed explanation” means don’t just give a one sentence answer. * Don’t forget to include your calculations and references!  Late assignments are not accepted for grading.

Questions: 1) Assume that you measure the OD of two E.coli cultures: culture A and culture B. The spectrophotometer gives you a reading of 2.2 for culture A and 0.02 for culture B. What would you do to determine the concentration of culture A and B and why? Give a detailed explanation!

For culture A the OD
…show more content…
At 11:30am the
OD of a 1:10 dilution of the stock culture was 0.29. For culture “Y”: 0.16 at
9:50am, 0.19 at 10:10am, 0.21 at 10:30, 0.24 at 10:50 am, 0.28 at 11:10am and 0.32 at 11:30am. A) Draw the two graphs. B) What was the generation time of these cultures? C) What could be the reason for the different growth pattern? Give a detailed explanation!

4) For a different experiment you are growing up Saccharomyces cerivisiae instead of E.coli. The measured OD is 0.89. A) In order to calculate the concentration of the Saccharomyces cerivisiae culture, can you use the equation that you use to calculate the concentration of an E.coli culture? If yes or no, give a detailed explanation. B) Does E.coli or Saccharomyces cerivisiae have a shorter generation time? Give a detailed explanation!

5) Your TA gives you an E.coli culture that has a concentration of 2000cells/ml. He/she tells you to evenly spread 25µl of this culture on an LB agar plate and another 25µl on a GMS plate. Both plates are incubated at 37oC. What do you expect to see the next day and why? Give a detailed explanation!

6) You want to determine what the optimal pH is for E.coli to grow. How would you set up the experiment? Give a detailed
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