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.