a)Suppose you neef to make a 10 -1 dilution of 2.0 mL of an E.coli culture. Expl

Question

a)Suppose you neef to make a 10-1 dilution of 2.0 mL of an E.coli culture. Explain how would you do this?

b)Suppose you neef to make a 10-2 dilution of 5.0 mL of an E.coli culture. Explain how would you do this?

c)You have 0.6 mL an undiluted culture at a density of 3.7 x 107 CFU/mL. You add 5.4 mL of sterile diluent. What is the final cell density?

d)What is the dilution if you add 160 mL of diluent to 40mL culture?

e) Plating 2.0 mL of a sample diluted by a factor or 10-2 procedures 56 colonirs. What was the original cell density in the sample?

f)Plating 0.2 mL of a sample diluted by a factor or 10-4 procedures 87 colonirs. What was the original cell density in the sample?

Explanation / Answer

A) If we need to make a 10-1 dilution of 2.0 mL of an E.coli culture then we have to add 2.0 mL of the E.coli culture into 18 ml of culture medium. The final dilution factor will be 10-1.

B) If we need to make a 10-2 dilution of 5.0 mL of an E.coli culture then we have to add 5.0 mL of the E.coli culture into 495 ml of culture medium. The final dilution factor will be 10-2.

C) The final cell density is 3.7 x 107 / 6 = 6.16 X 108 CFU/ml

D) If you add 160 mL of diluent to 40mL culture then the dilution is 5 times or 101/2.

E) There is 5600 colonies in original 2 ml of sample. Therefore, the cell density in sample is 2800 CFU/ml.

F) 87 X 104 colonies are there in 0.2 mL of a sample. Therefore, the original cell density in the sample is 5 X 87 X 104 = 435 X 104 = 4.35 X 106.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.