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Performing 5 10 fold liquid culture dilutions of bacteria?
You have a liquid culture of bacteria. You perform 5 10 fold dilutions and plate 0.1 mL on an agar plate. After the colonies grow up, you count 37 bacteria on the plate. What was the bacterial concentration in the original culture?
Please put how you got the answer as well. Thank you
1 Answer
- Simonizer1218Lv 77 years ago
Working backwards: 37 bac/0.1 m = 370 bac/ml
To account for the previous dilutions that were 10 fold, you have 10 x 10 x 10 x 10 x 10 = 10^5 fold
So, the original would have 10^5 x more bacteria/ml.
Thus, 370 x 1x10^5 = 370x10^5 bac/ml = 3.7x10^7 bacteria/ml (37 million bacteria/ml)
