Bacterial growth and metabolism
Binary fission & exponential growth
o Growth = an increase in the number of prokaryotic cells in a population
or an increase in prokaryotic mass
o Growth rate = the change in cell number or cell mass/unit time
o Generation = interval for the formation of 2 cells
o Generation time/doubling time = the time required for the formation
of 2 cells (from 1)
o Cell cycle/cell division in prokaryotes is overlapping i.e. S phase, G2 and cell
division all occurring at the same time
o Exponential growth = the number of prokaryotic cells doubles during
each generation time
o Measuring exponential growth: cell number plotted against elapsed
time, the result is a growth curve. If the info is plotted on semi-logarithmic
paper, the result is a straight line. This straight line is a) indicative of
exponential growth and b) can be used to calculate the doubling time of
the bacteria directly/by calculating slope
o Calculating Generation Times: prokaryotic populations increase
exponentially and there is a direct relationship between the no. of cells
present in a culture initially (N0) and the number present (N) after a period
of exponential growth (t)
- G = T/N
- G = generation time, T = time, N = (logN1-logN0)/log2, N0= number
at time 0, N1= number at first time point
- Example: What is the generation time of a bacterial population that
increases from 10,000 to 10,000,000 cells in 4 hours?
- = (log10,000,000-log10,000) /log2
- = (3) / 0.301
- =10
- g = t/n (t=240 min, n= logN1-logN0)/log2)
- g = 240/10 = 24 mins
Binary fission & exponential growth
o Growth = an increase in the number of prokaryotic cells in a population
or an increase in prokaryotic mass
o Growth rate = the change in cell number or cell mass/unit time
o Generation = interval for the formation of 2 cells
o Generation time/doubling time = the time required for the formation
of 2 cells (from 1)
o Cell cycle/cell division in prokaryotes is overlapping i.e. S phase, G2 and cell
division all occurring at the same time
o Exponential growth = the number of prokaryotic cells doubles during
each generation time
o Measuring exponential growth: cell number plotted against elapsed
time, the result is a growth curve. If the info is plotted on semi-logarithmic
paper, the result is a straight line. This straight line is a) indicative of
exponential growth and b) can be used to calculate the doubling time of
the bacteria directly/by calculating slope
o Calculating Generation Times: prokaryotic populations increase
exponentially and there is a direct relationship between the no. of cells
present in a culture initially (N0) and the number present (N) after a period
of exponential growth (t)
- G = T/N
- G = generation time, T = time, N = (logN1-logN0)/log2, N0= number
at time 0, N1= number at first time point
- Example: What is the generation time of a bacterial population that
increases from 10,000 to 10,000,000 cells in 4 hours?
- = (log10,000,000-log10,000) /log2
- = (3) / 0.301
- =10
- g = t/n (t=240 min, n= logN1-logN0)/log2)
- g = 240/10 = 24 mins
