Question

A common inhabitant of human intestines is the bacterium Escherichia coli, named after the German pediatrician Theodor Escherich, who identified it in 1885. A cell of this bacterium in a nutrient-broth medium divides into two cells every 20 minutes. The initial population of a culture is 50 cells.

Required:
a. Find the relative growth rate.
b. Find an expression for the number of cells after t hours.
c. Find the rate of growth after 6 hours. (Round your answer to the nearest integer.)
d. Find the number of cells after 6 hours.

Answer 1

a. Relative Growth rate = 10% (6/60 * 100)

b. Number of cells after t hours = 50 * 1.1^t

c. Rate of growth after 6 hours = 77.2% (1.1⁶ - 1)

d. The number of cells after 6 hours is

= 89 cells

Explanation:

A cell divides into two cells every 20 minutes

In one hour, the cell will divide into 60/20 * 2 = 6 cells

Each cell growth 6 cells per hour

Initial population of a culture = 50 cells

t = time in hours

a. Relative Growth rate = 10% (6/60 * 100)

b. Number of cells after t hours = 50 * 1.1^t

c. Rate of growth after 6 hours = 77.2% (1.1⁶ - 1)

d. The number of cells after 6 hours = initial population * growth factor

= 50 * 1.772

= 88.6

= 89 cells