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OBJECTIVES
•Identify the four phases of the growth
curve
•Calculate generation time
•Make use of the growth curve
Growth
• an orderly increase in cell number
cell division（细胞分裂）
• a developmental program superimposed
upon this increase
cell differentiation （细胞分化）
Binary Fission
Parent cell
Daughter
cell
Daughter
cell
1, 2, 4, 8, 16, 32, 64……
20, 21, 22, 23, 24, 25, 26……
一条典型的生长曲线至少可以分为迟缓期，
对数期，稳定期和衰亡期等四个生长时期。
Lag phase
making new enzymes in
response to new medium
Log phase
exponential growth
– Desired for
production of
products
– Most sensitive to
environment
Stationary phase
– nutrients becoming
limiting or waste products
becoming toxic
– secondary metabolism
– death rate = division rate
Death phase
death exceeds
division
N2
N1
t
世代时间
The generation time of a culture is defined as
A. the time it takes a cell to divide.
B. the time it takes the culture to begin growth.
C. the interval of time between the end of log phase to
the stationary phase of growth.
D. the period of time it took for the organism to appear
on earth.
E. how long the culture has been growing.
Bacterium
Medium
Generation Time (minutes)
Escherichia coli
Glucose-salts
17
Bacillus megaterium
Sucrose-salts
25
Streptococcus lactis
Milk
26
Streptococcus lactis
Lactose broth
48
Staphylococcus aureus
Heart infusion broth
27-30
Lactobacillus acidophilus
Milk
66-87
Rhizobium japonicum
Mannitol-salts-yeast extract
344-461
Mycobacterium tuberculosis
Synthetic
792-932
Treponema pallidum
Rabbit testes
1980
Calculation of Generation Time
G = t/n
G ---generation time (time for the cells to divide)
t---time (interval in hours or minutes)
n---number of generations
(number of times the cell population doubles
during the time interval)
N1 = number of bacteria at the beginning of a time interval
N2 = number of bacteria at the end of the time interval
N2 = N1 × 2 n
(This equation is an expression of growth by binary fission)
Solve for n
log N2 = log N1 + nlog2
n = log N2 - log N1
log2
n = log N2 - log N1
0.301
n = 3.3 log N2/ N1
Solve for G
G = t/n
G=
t
3.3 log N2/ N1
A bacterium with a generation time of 0.5
hours will grow from a population of 103 to 109
cells, in about how many hours?
A. 25
B. 3
C. 40
D. 20
E. 10
Solve for G
G=t/n
G=
t
3.3 log N2/ N1
Use of the
Growth curve
•Bacteria from_______ phase can served as “seed” to another
culture medium effectively, to decrease the lag phase
•Bacteria from_______ phase have the most typical morph－
ological, biochemical and physiological features
•Bacteria from_______ phase can be used to screen medicine
If at time 0 you had 10 million cells and two
hours later had 40 million cells, what is the
generation time?