Question

After measuring the OD (see question 5) of an S.aureus bacterial culture, you find that the concentration is too high and perform a 1:1 dilution. In order to reach a final volume of 1000uL in your cuvette, what combination of bacterial culture and fresh media must be combined to achieve the desired dilution? If the OD after the dilution is 0.54, what was the undiluted OD?

(question 5: After you have grown a culture of E. coli bacteria, you measure the optical density (OD, this is the same as absorbance and used to measure bacterial concentration) in a spectrophotometer and find that the OD is 0.8. You want an OD of 0.4, and decide to dilute your culture. After pelleting 500 µL of bacteria using the micro-centrifuge and removing the supernatant, what volume of media is required to re-suspend your bacteria in to achieve the desired concentration? What is the dilution factor of your dilution?)

Answer 1

Answer:

Dilution factor (DF) calculated as =initial conc. / final conc.

Dilution factor (DF) calculated as = Final volume/initial volume

5):

• Here the final OD is 0.4 and the initial OD 0.8. So you have to 0.8/0.4 = 2 times dilute the bacterial culture.
• No, as per the given question, the volume of the bacterial culture was 500µl. So, after centrifugation, the pellet should be diluted in 500 µl * DF = 1000 µl

So, 1000 µl is required to resuspend the bacteria to achieve the desired concentration. The dilution factor is 2.

Please Rate My Answer...... Thank.....u...