Growth Cell Chapter 6 I. Binary Fission
A. DNA Replication B. Formation of Divisome
1. FtsZ 2. FtsA
C. Cell Elongation
1. FtsI 2. FtsK 3. MreB
D. Septum Formation E. Cell Separation
II. Autolysins
A. Autolysis
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III.Cell Wall Synthesis
A. N-acetylglucosamine / N-acetylmuramic acid / pentapeptide B. Bactoprenol
C. Transpeptidation
IV.
Growth Cycle
A. Growth Phases
1. Lag 2. Exponential 3. Stationary 4. Death
B. Generation ( C. Exponential Growth
Time (hours)
) Time
Total Number of Cells
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1. Semi logarithmic graph 2. Practical implication of exponential growth
3. Mathematics of exponential growth
N = No2n = final number of cells g = t/n = generation time No = initial number of cells n = number of generations t = time of exponential growth (hr, min)
4. Example: E. coli culture
Growing exponentially for 3 hours Started with 5 cells Generation time of 20 minutes
a) How many generations of E. coli are in the culture?
b) What is the final cell number of the E. coli culture?
D. Batch culture
E. Chemostat
1. Growth-limiting nutrient 2. Dilution rate
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V. Ways to Measure Growth
A. Cell Counts
1. Total Cell Count
a) Hemocytometer (counting chamber)
2. Viable Count
a) Spread plate method b) Pour plate method
B. Turbidity
1. Spectrophotometer
2. Growth Curves
3. Practical application example: E. coli culture
Initial density of OD600 0.24 Generation time of 20 minutes
a) How long will it take for this culture to reach OD 600 0.60?
4. Standard Curve
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C. Natural Samples
1. Great plate count anomaly
VI.
Environmental Effects on Microbial Growth
A. Temperature
1. temperatures
a) Cardinal Minimum b) Optimum c) Maximum
2. Psychrophiles - ____________ temperature optima
Ex. Chlamydomonas nivalis (http://home.nc.rr.com/redsnow/nivalis.htm)
a) Molecular adaptations to psychrophily
(1) (2) (3) (4)
b) Cryoprotectant
Examples: 10% Dimethylsulfoxide (DMSO); 10% glycerol
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3. Mesophiles - _______________ temperature optima
4. Thermophiles - _____________ temperature optima
a) Molecular adaptations to thermophily
(1) (2) (3) (4)
B. pH
1. pH range 2. pH optimum
a) Acidophiles grow best at ________ pH
b) Neutrophiles grow best at _________ pH c) Alkaliphiles grow best at ________ pH
3. pH buffers
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C. Osmolarity
1. Osmosis
a) Isotonic
b) Hypotonic
c) Hypertonic
2. Osmophile a) Halophile
Example: Vibrio natriegens b) Extreme Halophile
Example: Halobacterium salinarium c) Halotolerant
Example: Staphylococcus epidermidis
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D. Oxygen
1. Enviroment
a) Oxic environment _____________ oxygen. b) Anoxic environment ___________ oxygen.
2. Microorganism
a) Aerobes
(1) Obligate Ex. Bacillus subtilis (2) Microaerophilic Ex. Helicobacter pylori (3) Facultative Ex. Staphylococcus aureus
b) Anaerobes
(1) Obligate Ex. Clostridium tetani (2) Aerotolerant Ex. Psychromonas antarticus
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3. In the laboratory...
a) Reducing agent
(1) Thioglycolate broth
b) Aerobes
c) Anaerobes
4. Toxic Forms of Oxygen
a) Singlet oxygen O2 b) Superoxide anion O2c) Hydrogen peroxide H2O2 d) Hydroxyl radical OH
5. Enzymes
a) Catalase b) Peroxidase c) Superoxide Dismutase d) Superoxide Dismutase / Catalase in combination e) Superoxide Reductase
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