Question

Suppose you have a culture growing in logarithmic phase and find that there are 7x10⁵ CFU/ml initially and after 2 hours there are 5.6x10⁶ CFU/ml. Calculate the generation time for the bacteria (please list it in minutes, not hours). Show your work for partial credit

Answer 1

Answer:

Culture growing exponentially in log phase, the increase in bacterial population happens by Geometric Progression.
That is to say 1 cell becoming 2; 2 cells becoming 4; and 4 cells becoming 8... so on and so forth.

Generation Time is the time interval required for the cell (or entire population) to divide. In other words, it is the time required each time for the population to double.

Mathematically:

G = t / n

Where:
G = Generation Time
t = time interval
n = number of generations.

To calculate the number of generations elapsed, we need the following formula

n = log B2 - Log B1 / Log 2

Where:

n = we know is the number of Generations
B1 = number of bacteria in the beginning of time interval
B2 = number of bacteria at the end of time interval

So we first calculate the number of generations and then the Generation time.
both calculations are as shown under for the given data.

Having calculate number of generations in the time period, we now calculate the Generation Time: