Homework SourseA culture of Ecoli was grown overnight in a 37 degrees Celsi
A culture of E.coli was grown overnight in a 37 degrees Celsius shaking incubator. The OD read in a Spec 20+ was 1.0. Based on the standard curve the CFU/ml is 8 x 10^8.
1. Determine the dilution to be plated. Based on the dilution, determine the dilution factor and associated volume plated. Provide at least 2 alternatives. Show work
2. Draw the dilution scheme.
Solution
1) According to formula :
CFU/ml = number of colonies per ml plated /Total dilution factor
As we know CFU/ml = 8 x 10^8, we could have :
1st alternative : 80 colonies per ml plated / 10-7 Total dilution factor
2nd alternative : 800 colonies per ml plated / 10-6 Total dilution factor
(It could also have been 8 colonies / 10-8 dilution factor but it is very difficult to isolate and culture 8 colonies so we have considered 80 and 800 colonies)
2) Dilution Scheme:
I###I (Stock solution) ---> 0.1 ml + 9.9 ml dilution = 0.1/10.0 = 10-2 (A) ---> 0.1 ml + 9.9 ml Dilution = 0.1/10.0 = 10-2 (B)---> 0.01 ml + 9.99 ml dilution = 0.01/10 = 10-3 (C)
Individual Dilution factor of :
(A) = 10-2
(B) = 10-2
(C) = 10-3
Overall Dilution factor = mutlitplication of sequential dilution factors
(A)= 10-2
(B) = (10-2) (10-2) = 10-4
(C) = (10-2) (10-2) (10-3) = 10-7
