in this video you will learn how to quantify the concentration of bacteria in a culture using the serial dilution and plate count method label seven sterile microcentrifuge tubes with the dilution factor 10 to the first 10 to the second 10 to the third 10 to the fourth 10 to the fifth 10 to the 6 and 10 to the seventh next labels 7 lb agar plates on the bottom edge with the dilution factor 10 to the first ten to the second ten to the third 10 to the fourth 10 to the fifth 10 to the sixth and 10 to the seventh using a 100 to 1000 microliter micropipette set the volume to 900 microliters using aseptic technique pipette 900 microliters of lb broth into each micro centrifuge tube you next using a 20 to 200 microliter micropipette set the volume to 100 microliters using aseptic technique pipette 100 microliters of bacteria culture into the micro centrifuge tube labeled 10 to the first you mix by vortexing or pipetting up and down at least five times you remove 100 microliters of diluted cell culture from the tube labeled 10 to the first and add it to the tube labeled 10 to the second mix by vortexing or pipetting up and down at least five times continue to see really dilute the bacterial culture into each consecutive tube until the tube labeled ten to the seventh is used you mix the diluted cell culture in the tube labeled ten to the first and using aseptic technique pipette 100 microliters onto the LB outer plate labeled 10 to the first you sterilize an inoculation loop or bacterial spreader by flaming and then allow it to cool very gently spread the bacterial culture over the entire surface in all directions including the edge of the plate do not use the streak plate technique because you are not isolating for single colonies you plate 100 microliters of each dilution on the matching plate as in this example when finished stacked the plates upside down in place and an incubator at 37 degrees Celsius for 16 to 24 hours after 16 to 24 hours your place will be ready for analysis of results you