Post on 17-Jan-2016
Microbiology
List 2 examples of physical requirements and 2 examples of chemical requirements of bacterial growth in the lab.
Temperature
Figure 6.1
Figure 6.2
pHMost bacteria grow between pH 6.5 and 7.5Molds and yeasts grow between pH 5 and 6
The Requirements for Growth: Physical Requirements
The Requirements for Growth: Physical Requirements
Osmotic PressureHypertonic
environments, increase salt or sugar, cause plasmolysis
CarbonStructural organic molecules, energy source
NitrogenIn amino acids, proteinsMost bacteria decompose proteins
The Requirements for Growth: Chemical Requirements
SulfurIn amino acids, thiamine, biotin
Phosphorus In DNA, RNA, ATP, and membranes
Trace ElementsInorganic elements required in small amounts
Organic Growth FactorsOrganic compounds obtained from the
environmentVitamins, amino acids, purines, pyrimidines
The Requirements for Growth: Chemical Requirements
Oxygen (O2)
The Requirements for Growth: Chemical Requirements
obligate aerobes
Facultative anaerobes
Obligate anaerobes
Aerotolerant anaerobes Microaerophiles
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?
Microbial Characteristics and Microbial Control
Figure 7.11
Gram negative bacteria are more resistant to biocides than Gram positive
Due to:Lipopolysaccharides in outer membrane layerSome can grow in cleaning agents
(Pseudomonas)Porins (structural openings) selective to
passage of material
Most effective chemical control agents BiguanidesHalogens (iodine, chlorine bleach)Aldehydes (formaldehyde, gluteraldehyde)
Do antibacterial soaps really work better than regular soap? What evidence is there to support your answer?
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 2001. HowStuffWorks.com. <http://health.howstuffworks.com/skin-care/cleansing/myths/question692.htm> 20 June 2011.
How has the introduction of antimicrobial products increased microbial resistance? Should we as a society move away from the use of these products?
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 http://www.cdc.gov/ncidod/eid/vol7no3_supp/levy.htm 20 June 2011
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 http://www.cdc.gov/ncidod/eid/vol7no3_supp/levy.htm 20 June 2011
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.