Question

2. The CFU count on an agar diluted from the original sample by 10-8 is 400....

2. The CFU count on an agar diluted from the original sample by 10-8 is 400. What is the original cell density?

A. 4.0 x 10 to the 7th power

B. 0.4 x 10 to the 7th power

C. 4.0 x 10 to the 8th power

D. TNT

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Answer #1

TNT is the original cell density

because we used colony count range in between 30 to 300 for CFU calculation (30 to 300 range is statistically significant )

an even if we take 400 colony count for calculation then it will be as follows

we know the formula

CFU/ml= number of colonies on plate x dilution factor / volume plated

number of colonies = 400, dilution factor = 10^8, volume plated is not given so that we take 1ml

so that ,

CFU/ml= 400 x 10^8/1

CFU/ml= 400 x 10^8 = 4.0 x 10^10

if we take 400 colony count for calculation then there are = 4.0 x 10^10 CFU/ml is the original cell density

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