evens only pls 16 You imocuiated a mutrient agar plate with 100 L sample you cou
ID: 132280 • Letter: E
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evens only pls
16 You imocuiated a mutrient agar plate with 100 L sample you count 58 colonies, What was the original cell density d wmt aur plate with 100 l, of s mple diluted by a facr of 10 After mncabation, A nutrient agar plate labeled 10- ml produced 154 colomies after incubution. a. What was the cell density in the original samplet h. What combinationis) of volumes and dilution factors could have been wsed to inoculate this platet 18 A nutrient agar plate labeled 1O mL produced 62 colonies after incubation a. What was the cell density in the original samplet h. What combinationis) of volumes and dilution factors could have been used to inoculate this platet 6 19 The original cell density 1" a sample is 2.79 ×10°CFUn 1 platet (Express your answer as 10 mL) which samp lev lume sho uld yidd a comtable The original cell density in a sample is 5.1 x 10 CFUmL. Which sample vohone should yield a countable platet (Express your answer as 10 mL) 20 21 A sample has a density of 1.37 X 101 CFU/mL a. What sample volame should yield a countable plate b. Which two dilution tubes could be used to produce this sample volumet How 22 A sample has a density of 79 x 10° CFUml a. What sample volume should yield a countable plate b. Which two dilution tubes could be wsed to produce this sample solamet HowtExplanation / Answer
16. Cell density(cfu/ml) is calculated by: No. of colonies x dilution factor/(volume of sample inoculated)
Therefore in the given question, the Volume of sample inoculated = 100 ul = 0.1 ml
Dilution factor = 103
No. of colonies counted = 58
Therefore, original cell density = 58 x 103/(0.1) = 5800 CFU/ml or approximately
18. Given, the volume inoculated multiplied by the dilution= 10-7 ml
The number of colonies = 62
(i) The CFU of the original inoculum = 62 x 107=6.2 x 108 CFU/ml
(ii) The combinations of volume and dilution factors used can be: 100 ul with 10-8 dilution, 1000 ul with 10-7 dilution
20. Given original cell density= 5.1 x 109 CFU/ml
For a plate to have countable colonies, using the above original CFU inoculum
100 ul should be plated in 10-9 dilution. This would give 51 colonies on the plate.
22.
(a) Given original cell density= 7.9 x 109 CFU/ml
For a plate to have countable colonies, using the above original CFU inoculum, 100 ul should be plated in
10-9 dilution. This would give 79 colonies on the plate.
(b) The sample dilution tubes of 10-9 and 10-8 could be used to achieve this CFU/ml.
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