Use the following numbers to complete the exercise on serial dilutions. You have counted three plates that have a colonies growth on them. Note the dilution factors and calculate the approximate number of bacteria in the original volume of the test tube. -6 -7 -8 644 111 27 1702 289 13 357 85 9 OCD = CFU/D X V OCD = original cell density in scientific notation/ml CFU = colony forming units D = dilution written on the tube V = volume transferred onto the petri dish
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We can do this by multiplying the number of colonies on each plate by the dilution factor. Plate 1: 644 colonies x 10^-6 dilution factor = 6.44 x 10^-4 bacteria Plate 2: 111 colonies x 10^-7 dilution factor = 1.11 x 10^-5 bacteria Plate 3: 27 colonies x 10^-8 Show more…
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You perform 1 to 10 serial dilutions of a microbial culture and spread plate 100 μl of the diluted culture. After incubation, the plate counts are: 10^-0 TNTC 10^-1 TNTC 10^-2 490 colonies 10^-3 53 colonies 10^-4 8 colonies 10^-5 TFTC Using the formula: Count colonies (CFUs) present on plate, multiply by the dilution made, equals the number of cells in the original culture (CFU: Colony Forming Units). What is the concentration of the original culture? Answer choices: 4.9 x 10^5 CFU/ml 4.9 x 10^4 CFU/ml 4.9 x 10^3 CFU/ml 5.3 x 10^5 CFU/ml 5.3 x 10^4 CFU/ml 53 x 10^3 CFU/ml 490 x 10^3 CFU/ml
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