Problem
A. Robb Stark tried to complete 10-2 dilution in one dilution bottle, but placed 110mL of sterile water (diluent) into the tube instead of 99mL and then added 11mL of the sample (diluate). What was the actual dilution he produced?
B. Mowgli is counting yeast cells using the hemocytometer. He needs a dilution of 1:20 and 1:40 to be able to count the cells accurately, but without counting cells all day. Using a serial dilution and final volumes in tubes is 2 mL, how much yeast cell culture and sterile PBS (diluent) would she need to complete serial dilution of 1:20 and 1:40. * hint: serial dilution means 1/20 will be in the first tube & 1/40 will be the second tube.
C. If you have 9.3 mL of a diluent and you were supposed to add 760 ul but you accidentally added 76 µl instead. What was the actual dilution and intended dilution?
D. Tommen tried to make a 1/800 total dilution using 1/10 (tube dilution A), 1/10 (tube dilution B), and 1/8 (tube dilution C) in a serial dilution, but in tube A he added 0.1 mL of diluate into 9mL and then completed the rest of the dilution correctly. What was the actual dilution in the last tube (tube C)?
E. An entire 5mL of a bacterial sample needs to be diluted 2 x 10-3. How would you produce this dilution using the entire 5mL of the sample in one tube? Assessment Activity 1 (AA1): Dilution Problem Assignment Micro233L - Fall 2022
F. A plate dilution of 10-9 produced a total of 33 colonies. I. What was the original concentration in the sample? II. How many colonies should be on the plate inoculated with a sample volume of 10-8 using the same sample? III. How many colonies should be on the plate inoculated with a sample volume of 10-10 using the same sample
G. If a plate with 220 µl of a bacterial sample was diluted by a factor of 10-7 had 142 colonies after incubation. What was the original cell density?
H. A raw meat sample was diluted 10-3, then 0.1ml of the 10-3 cheese suspension was plated on plate count agar medium. After incubating for 48 hours at 370C, 104 colonies appeared.
a. What is the original concentration of this raw meat sample?
b. How many CFU per 0.1g of raw meat?
c. How many CFU per 0.01g of raw meat? Assessment Activity 1 (AA1): Dilution Problem Assignment.