Generation time

The generation time gives a good estimation of the health of your culture and the optimisation of the growth conditions. It will also enable you to estimate when a specific population size will be reached.

To calculate the generation time, you will need to measure the population size (N) at two different time points during the exponential phase, keeping in mind the interval t during these timepoints.

At population size at time point zero and time zero, one green rod shaped bacteria is shown. At population size at time point one and time 1, two of such bacteria are present. At population size 2 and time 2, four bacteria cells are shown. Finally, at population size at time point t and time at small n number of generations, there are tens of bacteria cells shown.

Let's call the population at the first timepoint N₀ and at the second timepoint N_t, with n the number of generations.

From the formula explained above:

N_t = N₀ x 2ⁿ (each cell at N₀ has doubled in each generation until reaching N_t)

Thus:

log(N_t) = log(N₀) + n x log(2)

We are looking for the number of generation n:

n = log(N_t) - log(N₀) / log(2)

n = log(N_t) - log(N₀) / 0.301

n = 3.3 x log(N_t / N₀)

By counting the population at N₀ and N_t you have now calculated the number of generations which occurred in the interval. By dividing the time of the interval t by the number of generations, you will get the generation time (for 1 generation).

G = t / n

Thus in one equation:

G = t / (3.3 x log (N_t / N₀)

Check out the growth rate constant page to learn how this relates the growth rate constant.

Referred from:

Article

Bacterial Growth