1. **Microbial Growth**
Growth= an increase in the number of cells, not an increase in size
Generation=growth by binary fission
Generation time=time it takes for a cell to divide and the population to double

2. Bacteria divide by binary fission

3. Generation times vary for each organism
E. coli
Mycobacterium tuberculosis

4. **Bacterial growth curve**
Know the phases of the bacterial growth curve what the X and Y axes represent. Be able to explain why the curve is shaped the way it is – i.e., what is happening in each of the phases and how that relates to bacterial growth. Also know the changes in production of primary and secondary metabolites at different stages in the growth curve.

5. *Primary and Secondary metabolites
I will ask you about secondary metabolites – know what they are, when they are produced and why.

6. **Requirements for bacterial growth**
Environmental factors that influence
Temperature, pH, osmotic pressure, oxygen
Nutritional factors
Carbon, nitrogen, sulfur, and phosphorous
Trace elements

7. *Optimum Growth Temperatures
Psychrophiles-optimum -5 to 15oC
Psychrotrophs- range from 20-30oC
Mesophiles- range from 25-45oC
Thermophiles-range from 45-70oC

8. Growth rates in different temperatures

9. pH influences the growth
Bacteria-prefer a pH range of
Molds prefer a pH range of

10. Osmotic environment influences growth

11. **Oxygen preferences of organisms**
Obligate aerobes require oxygen for growth
Facultative anaerobes: can grow in aerobic or anaerobic environments
Obligate anaerobes: unable to grow in the presence of oxygen

12. **Why can some organisms grow in the presence of oxygen?**
Because they have the ability to neutralize toxic oxygen molecules (superoxide, oxygen radicals)
Toxic forms of oxygen need to be neutralized by enzymes
Superoxide dismutase
Catalase

13. *Oxygen Preferences of Bacteria

14. Candle jars increase CO2 levels for growing capnophiles
How does a candle jar create a CO2-enriched/O2-depleted environment? Is it an anaerobic environment?

15. Anaerobic jars eliminate the oxygen for anaerobes to grow.
How does the hydrogen gas generator create an anaerobic environment?

16. Chemical requirements: Carbon
What are possible sources of carbon?
Bacteria are classified based on the source of carbon as either heterotrophs or autotrophs

17. Classification based on Energy and Carbon sources

18. Chemical Requirements: Nitrogen
Why do bacteria need nitrogen?

19. Chemical requirements: Sulfur and Phosphorous
Why do bacteria need sulfur?
Why do bacteria need phosphorous?

20. Chemical requirements: trace elements
Small amounts of minerals
Usually function as cofactors

21. *Culture Media Chemically defined GSA
A chemically defined medium is one where we know EXACTLY what the ingredients are. An undefined medium is one where we don’t know the exact chemical makeup (for instance, it may contain “protein digest”

22. Chemically defined media

23. Culture Media
Complex
Nutrient Agar
TSA
BHI

24. *Culture Media
Selective
Differential
Selective and Differential

25. *Ways to measure bacterial growth
Direct Count
Plate Count/Viable Cell Count
Measure Turbidity

26. Direct Counts

27. Plate counts require dilutions to obtain colonies

28. Plate Counts: pour plate

29. Plate Count-spread plate

30. *Turbidity gives a rough estimate