Microbial Growth Website

IBERS: Institute of Biological, Environmental and Rural Sciences

Workings for v and g Question

Correct answers:

i) v = 2.3 divisions/hour

ii) g = 0.43 hours (i.e. 25.8 minutes)

The workings for the problem are as follows:

(i) Calculate the growth rate v.

During 7 hours of  unrestricted exponential growth the cell numbers increased from 5000 cells to 4x10⁸ cells. The number of divisions (n) that occurred during those 7 hours is given by:

n = [log₁₀(4x10⁸) – log₁₀(5000)] / log₁₀(2) = 16.29

If 16.29 divisions (n) occurred in 7 hours (t) then the number of divisions per hour  (growth rate, v)  is given by:

v = n / t

v = 2.3 divisions / hour

(ii) The generation time (g) is calculated using:

g = 1 / v

g = 1 / 2.3

g = 0.43 hours (i.e. 25.8 minutes)