Exam2_rev-sp08-3 - Controlling Microbial Growth I. Physical...

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Controlling Microbial Growth I. Physical Control: A. Heat 1. how does heat kill microbes? - bacteria cannot tolerate extreme temp changes 2. is boiling enough to kill all microbes? - no, pressure often needs to be used 3. how does an autoclave work? As the container is heated the pressure rises due to the constant volume of the container (see the ideal gas law). The boiling point of the water is raised because the amount of energy needed to form steam against the higher pressure is increased. 4. what types of items get autoclaved? -medical instruments, microbial media, anything metal (some plastics) B. Radiation 1. how does UV light kill microbes? Causes t-t dimers cell death bump forms on dna molecule (covalent bonding) 2. what is ionizing radiation? - solar rays, radioactive, 10K times more energy than UV - ionization of water (splitting of water) - DNA breaks apart - sterilize plastics, food, destroy viruses (ebola) 3. how does ionizing radiation kill microbes? C. Desiccation – how does it help prevent microbial growth? - removal of water, all living things need water D. Refrigeration / Freezing 1. Do these methods kill microbes? - microbes still there, cold temp slows down, microbes can freeze/ thaw and still reproduce II. Chemical Control: A. Disinfectants/ Antiseptics 1. Who was Joseph Lister? What was his contribution to microbiology? - studied Pasteur, soaked instruments in pheno B. Chemicals: understand how each of the following kill microbes and where they are used. 1. iodine- detergent (betadine) 2. chlorine- gas to disinfect H2O 3. silver nitrate- eyes infections (gonorrhea) 4. phenol III. Antibiotic Control 1. What did Fleming discover? Who was Erlich? - Fleming- penicillin, extract gram pos bacteria - Erlich- arsenic compounds as syphilis treatment 2. How do sulfa drugs work? - causes absence of folate which makes cells unable to
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divide (bacterial infections) “proof of conecpet 3. How does penicillin work? How was it isolated? - mold,
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This note was uploaded on 05/03/2008 for the course MBI 121 taught by Professor Balish during the Spring '08 term at Miami University.

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Exam2_rev-sp08-3 - Controlling Microbial Growth I. Physical...

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