1. Unit 3 Seminar
Microbiology

2. List 2 examples of physical requirements and 2 examples of chemical requirements of bacterial growth in the lab.

3. Temperature
Figure 6.1

4. Figure 6.2

5. The Requirements for Growth: Physical Requirements
Most bacteria grow between pH 6.5 and 7.5
Molds and yeasts grow between pH 5 and 6

6. The Requirements for Growth: Physical Requirements
Osmotic Pressure
Hypertonic environments, increase salt or sugar, cause plasmolysis

7. The Requirements for Growth: Chemical Requirements
Carbon
Structural organic molecules, energy source
Nitrogen
In amino acids, proteins
Most bacteria decompose proteins

8. The Requirements for Growth: Chemical Requirements
Sulfur
In amino acids, thiamine, biotin
Phosphorus
In DNA, RNA, ATP, and membranes
Trace Elements
Inorganic elements required in small amounts
Organic Growth Factors
Organic compounds obtained from the environment
Vitamins, amino acids, purines, pyrimidines

9. The Requirements for Growth: Chemical Requirements
Oxygen (O2)
obligate aerobes
Facultative anaerobes
Obligate anaerobes
Aerotolerant anaerobes
Microaerophiles

10. In general, given what you know about Gram negative and Gram positive cells, why do you think Gram negative bacteria are more resistant to chemical control agents? Which chemical control agent(s) would be most effective against Gram negative bacteria?

11. Microbial Characteristics and Microbial Control
Figure 7.11

12. Gram negative bacteria are more resistant to biocides than Gram positive
Due to:
Lipopolysaccharides in outer membrane layer
Some can grow in cleaning agents (Pseudomonas)
Porins (structural openings) selective to passage of material

13. Most effective chemical control agents
Biguanides
Halogens (iodine, chlorine bleach)
Aldehydes (formaldehyde, gluteraldehyde)

14. Do antibacterial soaps really work better than regular soap
Do antibacterial soaps really work better than regular soap? What evidence is there to support your answer?

15. Soap works by mechanical action
Do antibacterial soaps really work better than regular soap? What evidence is there to support your answer?
Soap works by mechanical action
Antibacterial products require 2+ minutes to work
Some bacteria will develop resistance
Antibacterial products also kill beneficial bacteria
"Is antibacterial soap any better than regular soap?" 01 August HowStuffWorks.com. < 20 June 2011.

16. How has the introduction of antimicrobial products increased microbial resistance? Should we as a society move away from the use of these products?

17. Antibacterial Household Products: Cause for Concern
Purpose is to protect vulnerable patients, not the general public
Antibacterial products
-do NOT cure infections
-can select for resistant strains
- Kill normal flora
Levy, S.(2000) Antibacterial Household Products: Cause for Concern. Retrieved from June 2011

18. Should we as a society move away from the use of these products?

19. Questions?

20. References
Tortora, G., Funke, B., & Case, C. (2007). Microbiology: An Introduction (8th ed.). San Francisco, CA: Pearson.
Levy, S.(2000) Antibacterial Household Products: Cause for Concern. Retrieved from June 2011
Is antibacterial soap any better than regular soap?" 01 August HowStuffWorks.com. < 20 June 2011.