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Calculating%20Bacterial%20Growth

# Calculating%20Bacterial%20Growth - Calculating Bacterial...

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Calculating Bacterial Growth See textbook for more information 2 number of generations x initial number of bacteria = total # of bacteria present after n generations Example: Bacillus cereus divides every 30 minutes. You inoculate a culture with exactly 100 bacterial cells. After 3 hours, how many bacteria are present? In 3 hours, B. cereus will divide 6 times. Therefore, n = 6. 2 6 = 64 or 2x2x2x2x2x2 100 x 64 = 6,400 cells Using the same example, let’s say you have determined that your sample contains 6,400 bacterial cells. You know that it incubated 3 hours. How many generations have occurred? Number of generations = (log cells at end of incubation ) - (log cells at beginning of incubation ) / 0.301 Therefore, (log 6400) - (log 100) / 0.301 = (3.81 - 2) / 0.301 = 6 generations To calculate the generation time for a population: 60 min x hours / number of generations In this example: 60 min x 3 hours / 6 generations = 30 minutes per generation Practice Problems 1. You perform a serial dilution and determine that the original number of cells in your sample was 12, 000.

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