Question 2. You are given a yeast culture ofconcentration 1.8 x 1010 cfu/ml. You are asked to make a1.8 x 10-8 dilution from this stock culture. The volumesin your tube(s) should not exceed 10 ml and the volumes you pipetteshould not be less than 0.1 ml.
(i) What is the CDF for this dilution?
(ii) Given your volume constraints, can you do this dilution ina single step? If yes, show me how. If no, answer questions (iii)and (iv) below.
(iii) If no, demonstrate (draw or grid out) how you would set upthe dilution. For each step, indicate in an orderly fashion thefollowing information: V2, V1, diluentvolume, DF for each dilution step, CDF upto that step, yeast concentration at that step.
(iv) Is this a serial dilution or a dilution series?
(v) What volume should you plate from the 1.8 x 10-8dilution to get 81 colonies
Question 2. You are given a yeast culture ofconcentration 1.8 x 1010 cfu/ml. You are asked to make a1.8 x 10-8 dilution from this stock culture. The volumesin your tube(s) should not exceed 10 ml and the volumes you pipetteshould not be less than 0.1 ml.
(i) What is the CDF for this dilution?
(ii) Given your volume constraints, can you do this dilution ina single step? If yes, show me how. If no, answer questions (iii)and (iv) below.
(iii) If no, demonstrate (draw or grid out) how you would set upthe dilution. For each step, indicate in an orderly fashion thefollowing information: V2, V1, diluentvolume, DF for each dilution step, CDF upto that step, yeast concentration at that step.
(iv) Is this a serial dilution or a dilution series?
(v) What volume should you plate from the 1.8 x 10-8dilution to get 81 colonies
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FOR #4 A & B I don't know if I did it correctly.....Please check & the other questions I'm having a heard time on. Thanks!
A. You have been given a tube of E. coli. You are asked to make 1 mL total volume of 10-1 dilution of the bacterial culture. Explain how you would do this. Show all necessary calculations.
____ ml cells + _____ ml water = 1 ml (total volume)
V1 D1 X V2 D2
1 mL X 1 = V2 X 10^-1
V2 = 1 mL/10^-1 so V2 = 10 mL.
But because V1 is part of V2. The answer is: 10 mL-1 mL= 9 mL of diluent must be added.
V1 D1 X V2 D2
1 mL X 1 = V2 X 10^-2
V2 = 1 mL/10^-2 so V2 = 100 mL.
But because V1 is part of V2. The answer is: 100 mL-1 mL= 99 mL of diluent must be added.
You have bacteria at a concentration of 5 x 108 CFU/mL. You spread 1 mL of this sample on an agar plate to obtain isolated colonies. How many colonies do you expect to find the next day after incubation at 370C? Can you count these colonies? Can you use this plate for determining concentration?
A. You have bacteria at a concentration of 1 x 103 CFU/mL (in real life â you donât know this, but we are just working on math skills here). You transfer 1 mL of this sample into 9 mL of water and then spread 1 mL on a plate of agar. How many colonies do you expect to find the next day after incubation at 370C? Can you count these colonies? Can you use this plate for determining concentration?
You take 0.05 mL of a culture of bacteria at a concentration of 4 x 107 CFU/mL, and add 4.95 mL of water to it. What is the dilution that you have performed? What is the concentration of bacteria (CFU/mL) in the diluted culture?
A. You have diluted a sample by 1000 fold (1/1000) and plated 1 mL on an agar plate. You observe 55 colonies. What was the concentration of the original sample in CFU/mL?
A. A bacterial sample has a concentration of 3 x107CFU/mL. You make serial dilutions of 10-3 followed by 10-2 and 10-1 dilutions. You finally plate 1 mL of the last dilution on an agar plate and incubate it at 370C. What is the total dilution? How many colonies do you expect to see on the plate?
Total dilution:
# of colonies expected on plate:
C. This time, you see 10 times fewer colonies than you had expected to see.What could have gone wrong? How will you fix this problem?
A bacterial sample has a concentration of 2 x106 CFU/mL. Show a scheme of dilutions to obtain 30-300 colonies on a plate. Your scheme should contain the volume of diluent (sterile water), volume of sample transferred each time, the concentration of bacteria (CFU/mL) in each dilution. You can assume you are plating 1 mL of the dilution on plates of nutrient agar. See Figure 1 in protocol.
These are the results of the experiment described in the protocol. From the data shown in the results section of Standard Plate Count protocol, calculate the concentration of bacteria (CFU/mL) in the original sample of E. coli. Show your calculations. Hint: remember that we donât use plates that have less than 30 or more than 300 colonies to do these calculations.
