Name ________________________________________
Serial Dilution Lab
1. Blank the spectrophotometer using sterile LB broth in a clean cuvette.
2. Pipet about 500 uL of your E. coli sample into a clean cuvette and measure the absorbance at 600 nm.
3. Using the approximate cells/mL from the spectrophotometer reading, design a dilution scheme that should
theoretically give you colony counts in the 1s, 10s, and 100s.
4. Get your dilution scheme approved by Mr. Ward and then perform the serial dilution.
How many hours did your E. coli culture incubate in the shaking water bath? _______________ hrs.
According to the spectrophotometer O.D. 600 reading, approximately how many E. coli cells are in one mL of your
broth culture? _________________________________ cells/mL
Dilution scheme:
After incubating the LB plates for 48 hrs. count the colonies on each plate and determine the number of E. coli/mL in
your original LB broth culture.
Dilution __________
Dilution __________
Dilution __________
# of colonies ______
# of colonies ______
# of colonies ______
Final Answer = _____________________________ cells/mL