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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 The Requirements for Growth: Physical Requirements 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 Osmotic Pressure Hypertonic environments, increase salt or sugar, cause plasmolysis The Requirements for Growth: Chemical Requirements 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 (O ) 2 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 layer Some can grow in cleaning agents (Pseudomonas) Porins (structural openings) selective to passage of material Most effective chemical control agents Biguanides Halogens (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/skincare/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 Should we as a society move away from the use of these products? 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/skincare/cleansing/myths/question692.htm> 20 June 2011.