1.)Calculate the serial dilution factors: Tube A: 0.1 ml from original sample an
ID: 78929 • Letter: 1
Question
1.)Calculate the serial dilution factors:
Tube A: 0.1 ml from original sample and 9.9 ml diluent=
Tube B: 0.1 ml from tube A into 9.9 ml diluent=
Tube C: 1 ml from tube B into 9 ml diluent=
Tube D: 1 ml from tube C into 9 ml diluent=
2.) If 0.1 ml from tube D was spread onto one plate resulting in 108 CFUs, calculate the original cell density(include the equation and units)
I'm having problems understanding standard plate count, mainly the calculations part. So if you could please explain how you got the answers that would be awesome
Explanation / Answer
1.)Calculate the serial dilution factors:
Tube A: 0.1 ml from original sample and 9.9 ml diluent=0.1/(0.1+9.9)= 1/100
Tube B: 0.1 ml from tube A into 9.9 ml diluent=1/100
Tube C: 1 ml from tube B into 9 ml diluent=1/10
Tube D: 1 ml from tube C into 9 ml diluent=1/10
Total dilution factor = 1/100 x 1/100 x 1/10 x 1/10 = 1/10^6
2.) If 0.1 ml from tube D was spread onto one plate resulting in 108 CFUs, calculate the original cell density(include the equation and units)
Original CFU/ml =
Dilution factor= 1/10^6
Number of colonies= 108
Volume of sample = 0.1 mL to the plate
cfu/ml = (no. of colonies)/ (dilution factor x volume of culture plate)
=108 (1/10^6 x 0.1)
= 108 x 10^7
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