Reference no: EM132391375
1. A. You were asked to take 1 mL of an undiluted sample and add 99 mL of water to it. Instead you took 0.1 mL of the sample and added 9.9 mL of water to it. What dilution were you asked to make and what was the actual dilution that you made?
B. Your friend took 10 mL of the sample and added 90 mL of water to it. What dilution did he perform?
C. Which sample was more dilute? Your sample or the one your friend made?
2. A. You have diluted a sample by 1000 fold and plated 1 mL on an agar plate. You observe 35 colonies. What was the concentration of the original sample in CFU/mL?
3. A plate has 48 colonies. This was obtained by diluting a bacterial sample to 1:10,000 and plating 1 mL of the 1:10-4 dilution. What is the concentration of the original bacterial sample?
4. A. A bacterial sample has a concentration of 2 x105CFU/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. How many colonies do you expect to see on the plate?
B. You see 10 fold more colonies than you had expected to see. What could have gone wrong? How will you fix this problem?
B. You see 10 fold less colonies than you had expected to see. What could have gone wrong? How will you fix this problem?