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Microbe Control

Microbe Control. Environmental Controls Temperature Radiation Pressure pH Moisture Control Methods. Temperature. Growth Temperature Maximum Optimum Minimum Heat Cold. Thermocrinis ruber. Radiation. Blue Light UV X-rays Gamma Rays Photoreactivation. Deinococcus radiodurans.

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Microbe Control

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  1. Microbe Control • Environmental Controls • Temperature • Radiation • Pressure • pH • Moisture • Control Methods

  2. Temperature • Growth Temperature • Maximum • Optimum • Minimum • Heat • Cold Thermocrinis ruber

  3. Radiation • Blue Light • UV • X-rays • Gamma Rays • Photoreactivation Deinococcus radiodurans

  4. Pressure • Piezophile • Barophile • Obligate barophiles • Pseudomonas bathecetes

  5. pH • Most • Marine • Molds vs. Bacteria • Molds like lower pH than bacteria • Acidophiles Acidic mud pot in Yellowstone Park – home to the acidophile Sulfolobus acidocaldarius. Credit: US National Park Service http://www.brooklyn.cuny.edu/bc/ahp/CellBio/Growth/MGpH.html

  6. Moisture • Bacteria vs Molds • Bacteria like more moisture than molds • Food Preparation • Dried Foods • Freeze-Dried Foods • “Cured” Foods

  7. Microbe Control Methods • TERMS: • Sterilize • Kill or remove all life present • Disinfect • Kill pathogens present • Germicide • Antiseptic • Sanitize • Make safe to use or eat from

  8. Ways to Sterilize & Disinfect STERILIZE • Burning • Boiling • Autoclave (pressure cook) • Filtration • Irradiation • Chemicals • Iodine • Chlorine DISINFECT • Detergents/Soaps • Acids & Bases • Alcohols • Mercury • Cresols • Hydrogen peroxide • Formalin • Antibiotics

  9. Pasteurization • Louis Pasteur • Internal temperature • Batch (Vat) • HTST • UP

  10. Growth (Culture) of Microbes • Natural media • Extracts • Infusions • Synthetic media • Nutrient broth • Nutrient agar

  11. Broth Solidifiers Which is useful for incubation at human body temperature? Gelatin Animal protein Melts @ 20°C Digested by microbes Agar Plant carbohydrate Melts @ ~100°C, solidifies @ ~42°C NOT digested by (terrestrial) microbes

  12. Culturing Techniques • Researchers use specific compounds and substrates in the culture medium and observe what grows! • MacConkey agar • Isolates enteric, Gram-negative, bacteria based on their ability to ferment lactose

  13. SIM Test • S = Sulfur reduction • I = Indole production • Kovac’s reagent • M = Motility

  14. Simmons Citrate Test • Tests the ability of certain organisms to utilize citrate as a carbon source. • pH indicator = Bromthymol blue • pH > 7.5 turns royal blue • Neutral pH green (just like uninoculated media)

  15. Christensen Urea Test • Some bacteria utilize urea, which results in the formation of ammonia. • Alkaline • Produces a red-pink/red-violet color • A negative reaction will have no color change and the agar medium will remain pale yellow.

  16. Identifying Specific Bacteria

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