SME
Microbiology
Microbial genetics
Use this for “120 colonies grow from 100 μL of 1000 μL of cells given 10 ng of plasmid. What is the transformation efficiency?”
Diagram
Cells
in
the
tube
=
colonies
×
tube
volume
volume
plated
=
120
×
1,000
100
=
1,200
This is an example. Type your own values to start a new problem.
n
Colonies on the plate
example
Vₚ
Volume plated
example
Vᵣ
Recovery volume
example
DNA
DNA used
example
T
Transformants in the tube
calculated
TE
Transformation efficiency
calculated · per μg
Formulas
T
=
n
×
Vᵣ
Vₚ
1,200
=
120
×
1,000
100
TE
=
T
DNA ÷ 1,000
1.20 ×
10
5
=
1,200
10 ÷ 1,000
Assumptions
•
Every colony on the selective plate grew from one transformed cell.
•
The cells were recovered in one tube, and the plate holds only the share spread on it.
•
Efficiency counts transformants per microgram of DNA added: 1 μg = 1000 ng.
Step-by-step
WE KNOW
n = 120, Vₚ = 100 μL, Vᵣ = 1,000 μL, DNA = 10 ng
FIND
transformants in the tube (T), transformation efficiency (TE)
Step 1 · Find transformants in the tube (T)
Use T = n × Vᵣ ÷ Vₚ
Scale the plate up to the whole tube.
T
=
120
×
1,000
100
T
=
120,000
100
T
=
1,200
Step 2 · Find transformation efficiency (TE)
Use TE = T ÷ (DNA ÷ 1,000)
Nanograms to micrograms (÷ 1000), then transformants per microgram.
TE
=
1,200
10 ÷ 1,000
TE
=
1,200
0.01
TE
=
1.20 ×
10
5
per
μg
Check
Put the numbers back in. Both sides should match.
1,200
=
120
×
1,000
100
✓
1.20 ×
10
5
=
1,200
10 ÷ 1,000
✓
Topic check
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