1. Culture Techniques
Strain - a microbial culture which is the descendent of a single cell originally isolated from the environment
Aseptic Technique- method of handling material without contamination from the environment

2. Nomenclature Binomial System Strain designation will not change
Genus species strain
Bacillus subtilis WKU009
Strain designation will not change

3. Bacterial colony
Figure 4.1

4. Inoculation Techniques
Two Forms of Medium
Broth - a liquid medium
Agar - a semi-solid medium
agar is chemical from seaweed that melts at 100C and freezes at 45C
Agar medium is used for the isolation of microbes- Streak Plates

5. Streak-plate method
Figure 4.2

6. Bacterial Growth An Increase in Population Number
Not an Increase in Cell Size

7. Cell Division Most Bacteria Reproduce by Binary Fission
The cell doubles in size
Replicates the chromosome (DNA)
Forms a septum in the center
Synthesizes a Cell Wall at the Septum
Daughter cells separate.

8. Binary fission
Figure 4.2

9. Bacterial Growth Curve
All microorganisms undergo similar growth patterns.
Each growth Curve has 4 Phases
1 Lag Phase
occurs immediately after inoculation
cells do not grow; cells per volume do not increase

10. Microbial Growth Curve
# cells / ml
Lag
Time

11. Microbial Growth Curve
Log
# cells / ml
Lag
Time

12. Microbial Growth Curve
2.) Growth Phase
Exponential Phase
Log Phase
During this phase the microbe is growing at the maximum rate possible.
Cells per volume increases dramatically
Most research is performed on cells during log phase

13. Microbial Growth Curve
Stationary
Log
# cells / ml
Lag
Time

14. Microbial Growth Curve
3.) Stationary Phase
Growth levels off.
Cells per volume does not increase or decrease
Growth Rate = Death Rate
Due to
Depletion of Nutrients
Increase in Waste Products

15. Microbial Growth Curve
Stationary
# cells / ml
Log
Death
Lag
Time

16. Microbial Growth Curve
4.) Death Phase
Death Rate exceeds Growth Rate
Cells per volume decreases
Due to:
Very low concentrations of Nutrients
Very high concentrations of Waste Products

17. Nutritional Requirements for Microorganisms
WATER
ENERGY
CARBON
ESSENTIAL ELEMENTS

18. Nutritional Requirements for Microorganisms
WATER-
water serves as a solvent to carry nutrient to and waste products away from the cell
One method preservation of a microbial culture is drying (desiccation).

19. Energy Sources Phototroph- energy from sunlight
Chemotroph- energy from chemicals
Chemoorganotrophs [organotrophs]- derive energy from ORGANIC CHEMICALS
Chemolithotrophs [lithotrophs]- derive energy from INORGANIC CHEMICALS

20. Carbon Sources
Autotrophs- carbon from carbon dioxide (CO2) - Inorganic carbon
Heterotrophs- carbon from Organic Carbon
Ex. Carbohydrates, lipids, protein

21. Essential Elements
Hydrogen (H), sulfur (S), Oxygen (O), Phosphorus (P),
Nitrogen (N)
commonly supplied as ammonia (NH4)
some microbes “fix” atmospheric nitrogen (N2)
Trace Elements
required in SMALL amounts
Copper (Cu), Zinc (Zn), Selenium (Se)

22. “Extra” Growth Factors
Fastidious Microorganisms
microbes which need special organic chemicals added to the medium for growth to occur
Ex. Vitamins, amino acids

23. Environmental Requirements for Growth
Temperature pH
Oxygen
Carbon Dioxide
Osmotic Pressure
Hydrostatic Pressure

24. Temperature Psychrophiles - optimum less than 20°C
Mesophiles- optimum 20-45°C
Thermophiles- optimum 45-80°C
Extreme Thermophiles- optimum 85+°C

25. Temperature ranges
Figure 4.4

26. Molecular Oxygen (O2) Microbe vary greatly in sensitivity to O2
Aerobes- microbes which require O2.
Anaerobes- microbes which DO NOT utilize O2 AND are KILLED by O2
Facultative Microbes- microbes which can grow in presence OR absence of O2
Microaerophiles - required 3-15% O2

27. GasPak Fig. 5.12B O O O + 2 H H 2 H H Clamp with clamp screw
Platinum
catalyst O
Clamp with clamp screw
Oxygen in jar
(O2)
Water
(H2O)
Lid with O-ring gasket O
Catalyst pellets in
reaction chamber O +
Flash arrester to
prevent explosion 2 H H
GasPak disposable
hydrogen and carbon
dioxide generator
envelope
Hydrogen
gas (H2)
GasPak disposable
anaerobic indicator
strip
Culture plates
Copyright © 1996 The McGraw-Hill Companies, Inc.