1. Growth Curve

2. OBJECTIVES
Identify the four phases of the growth curve
Calculate generation time
Make use of the growth curve

3. 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）

4. Binary Fission 20, 21, 22, 23, 24, 25, 26…… Parent cell Daughter cell
1, 2, 4, 8, 16, 32, 64……
20, 21, 22, 23, 24, 25, 26……

6. 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。

7. Lag phase
making new enzymes in response to new medium

8. Log phase
exponential growth – Desired for production of products – Most sensitive to environment

9. Stationary phase – nutrients becoming limiting or waste products becoming toxic – secondary metabolism
– death rate = division rate

10. Death phase
death exceeds division

11. N2 N1 t

12. The generation time of a culture is defined as
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.

13. Generation Time (minutes)
Bacterium
Medium
Generation Time (minutes)
Escherichia coli
Glucose-salts 17
Bacillus  megaterium
Sucrose-salts 25
Streptococcus lactis
Milk 26
Lactose broth 48
Staphylococcus aureus
Heart infusion broth
27-30
Lactobacillus acidophilus
66-87
Rhizobium japonicum
Mannitol-salts-yeast extract
Mycobacterium tuberculosis
Synthetic
Treponema pallidum
Rabbit testes
1980

14. 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)

15. N1 = number of bacteria at the beginning of a time interval
N2 = number of bacteria at the end of the time interval
N2 = N1 × 2n
(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            log N2/ N1

16. A bacterium with a generation time of 0
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                    log N2/ N1

17. Bacteria from_______ phase can be used to screen medicine
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

18. If at time 0 you had 10 million cells and two hours later had 40 million cells, what is the generation time?