Table 1. Plate count results. TNTC = too numerous to...

Table 1. Plate count results. TNTC = too numerous to count. Dilution | Colonies (1st replicate plate set) | Colonies (2nd replicate plate set) 1/2 | TNTC | TNTC 10^-1 (1/10) | 455 | 424 10^-2 (1/100) | 40 | 38 10^-3 (1/1000) | 1 | 2 10^-4 (1/10,000) | 0 | 0 7. A flask of Klebsiella bacteria has been growing overnight, and you want to determine the number of cells (CFU) per ml in your flask by viable plate count. You make a series of dilutions, and prepare two agar plates (replicates) for each dilution (1 ml of dilution is spread on each plate). Based on the results shown in the above table, what is the CFU/ml of the original culture? A. 3.9 x 10^3. B. 3.27 x 10^3. C. 4.41 x 10^3. D. 1.5 x 10^4. E. 4.0 x 10^4.

Transcript

00:01 Hello students in this question we have given a formula for culture density so we have to find the cfu per ml in the sample of bacteria after one hour of growth and only using the counts between the 10 to 300 and find the average between these colonies so let's start with the answer the formula given is which is cfu per ml this is equals to number of colony but just divided by dilution factor multiplied by volume plated which is in ml.

01:04 So we have to calculate this.

01:06 So in the first, which is culture density in the sample after one of growth, it is cfu by ml.

01:17 This is equal to 499 divide by 10 raise to power 1, which is dilution factor for 499 and 0.

01:26 This is volume plated.

01:28 So this will be equals to 4 .99 into 10 days to power 4.

01:34 So this is the first value which is more than 300.

01:41 So this is not accurate and second value will be cfu per ml.

01:47 This will be 5 .18 10 x to power minus 1 which is one dilution factor and volume plated is 0 .1.

01:57 So this will be 5 .1.

01:58 To 5 .18 into 10 days to power 4 cfu per ml this is also greater than 300 so this data will also not be accurate and the third for cfu it will be 83 upon 10 days to power minus 2 into 0 .1 this will be equals to 8 .3 into 10 days to power minus 2 into 0 .1 this will be equals to 8 .3 into 10 days to power 4 cfu per ml and fourth will be cfu per ml this is equals to 8 point sorry 87 divide by 10 is to power minus 2 into 0 .1 which is volume so this is 8 .7 into 10 is to power 4 cfu per and fifth will be cfu per ml value this is equal to 10 to power sorry 10 by 10 to power minus 3 into 0 .1 which is equal to 1 into 10 to power 5 cfu per ml and for 6th the cfu per ml value this is equal to 8 by 10 to power minus 3 into 0 .1 which is equal to 8 into 10 inches to power 4 cfu per ml.

03:50 So by calculating these we can say this 3 to 5 value as the colony observed between 10 to 300.

04:03 The data is accurate...

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