Microbiology
List 2 examples of physical requirements and 2examples of chemical requirements of bacterialgrowth in the lab.
Temperature
Figure 6.1
Figure 6.2
pH
Most bacteria grow between pH 6.5 and 7.5
Molds and yeasts grow between pH 5 and 6
The Requirements for Growth:Physical Requirements
The Requirements for Growth: PhysicalRequirements
Osmotic Pressure
Hypertonicenvironments,increase salt or sugar,cause plasmolysis
Carbon
Structural organic molecules, energy source
Nitrogen
In amino acids, proteins
Most bacteria decompose proteins
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
The Requirements for Growth:Chemical Requirements
Oxygen (O2)
The Requirements for Growth:Chemical Requirements
obligateaerobes
Facultativeanaerobes
Obligateanaerobes
Aerotolerantanaerobes
Microaerophiles
In general, given what you know about Gram negativeand Gram positive cells, why do you think Gramnegative bacteria are more resistant to chemicalcontrol agents? Which chemical control agent(s)would be most effective against Gram negativebacteria?
Microbial Characteristics andMicrobial Control
Figure 7.11
Gram negative bacteria are more resistant to biocidesthan Gram positive
Due to:
Lipopolysaccharides in outer membrane layer
Some can grow in cleaning agents (Pseudomonas)
Porins (structural openings) selective to passage ofmaterial
Most effective chemical controlagents
Biguanides
Halogens (iodine, chlorine bleach)
Aldehydes (formaldehyde, gluteraldehyde)
Do antibacterialsoaps really workbetter than regularsoap? What evidenceis there to supportyour answer?
Do antibacterial soaps really workbetter than regular soap? Whatevidence is there to support youranswer?
-Soap works by mechanical action
-Antibacterial products require 2+minutes to work
-Some bacteria will developresistance
-Antibacterial products also killbeneficial bacteria
"Is antibacterial soap any better than regular soap?" 01 August 2001. HowStuffWorks.com. <http://health.howstuffworks.com/skin-care/cleansing/myths/question692.htm> 20 June 2011.
How has the introduction of antimicrobial productsincreased microbial resistance? Should we as a societymove away from the use of these products?
Antibacterial Household Products: Cause for Concern
Purpose is to protect vulnerablepatients, 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 http://www.cdc.gov/ncidod/eid/vol7no3_supp/levy.htm 20 June 2011
Should we as a society move awayfrom the use of these products?
References
Tortora, G., Funke, B., & Case, C. (2007). Microbiology: AnIntroduction (8th ed.). San Francisco, CA: Pearson.
Levy, S.(2000) Antibacterial Household Products: Causefor Concern. Retrieved fromhttp://www.cdc.gov/ncidod/eid/vol7no3_supp/levy.htm20 June 2011
Is antibacterial soap any better than regular soap?" 01August 2001. HowStuffWorks.com.<http://health.howstuffworks.com/skin-care/cleansing/myths/question692.htm> 20 June 2011.