Lecture 13: Control of Microbial Growth (Quiz 7)

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Lecture 13: Control of Microbial Growth (Quiz 7)
2015-05-22 16:11:43
The controlling of microbial growth
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  1. Filtration
    • Good for large quantities
    • Bugs stuck on the filter, that is what's plated
  2. Dry Weight Measurement
    • A type of measurement
    • Dehydrating the bacteria into powder
  3. Spectrophotometer
    • It detects tube turbidity
    • The most common form of measurement
    • Living and dead cells
    • A lightbulb shines through the tube on the inoculated and uninoculated, and detects how much turbidity is in each by how much the light is able to pass through.
  4. Sterilization
    • Everything is dead
    • The killing or removal of all microorganisms in a material or on an object
    • There are no degrees on sterillity, it is either sterile or not
  5. Disinfection
    • Reducing the numbers of microorganisms in or on an object so they pose no threat of infection
    • Disinfectants: Refers to inanimate objects
    • Antispetics: Apply to living things
  6. Bacteriostatic
    An agent that inhibits the growth of bacteria
  7. Bacteriocide
    • An agent that kills bacteria
    • These agents, however, do not usually kill spores
  8. Time/Organic Matter
    • When there are fewer organisms, there is less time needed
    • Organic matter can inhibit the effectiveness of a compund
    • Clean instruments/object before sterilizing it
  9. Logarithmic Phase
    • Most susceptible
    • Rapidly dividing
    • Many proteins/enzymes at work
    • Many different items needed
    • Spores, Thick Cell Wall, Capsule, Biofilm: ALL of these will interefere with our ability to kill bacteria
  10. Thermal Death Point
    • Temperature that kills all the bacteria in a 24 hr broth culture at neutral pH in 10 min
    • The temp that is needed to kill
  11. Thermal Death Time
    • Time required to kill all bacteria in a culture at a specific temperature
    • What time is needed to kill
  12. Dry Heat
    • SLOWER than moist heat
    • Sterilization happens at 171C in one hour, 160C in two hours, 121C in 16 hours
    • Flaming loops and tubes
  13. Moist Heat
    • MORE PENETRATINGĀ due to water, widely used, good killer of microbes
    • Water heated under pressure = Higher boiling temperature
  14. Autoclave
    • Used for sterilization
    • Heats water under pressure for steam
    • Part of moist heat
    • Double atmospheric pressure
    • Boils at 121C
    • Can kill spores/viruses
  15. Test Kit with Spores
    • To see if the autoclave is working
    • A test tube with medium inside is surrounded by a strip with spores, put into the autoclave and then taken out. When removed, the medium in the center is crushed and is left to innoculate. If bacteria grows, the autocave is not working. If spores don't grow, they were killed
  16. Pasteurization
    • Destroys harmful microorganisms (but not all) without major changes in the chemistry of the food
    • HTST: High temp, short time (71.6C for 15 sec, Flash, Milk)
    • LTLT: Low temp, long time (62.9C for 30 min, Holding)
    • UHT: Ultra high temp (87.8C for 3 sec, sealed paper containers=6 months shelf life)
  17. Fitration (Part 2)
    • Generally a .22 filter is used
    • it passes samples through a filter to sterilizeĀ 
    • WHAT CAN'T: Red blood cells, bacteria
  18. Irradiation
    • Using light waves (UV also)
    • X-rays/Gamma: Damages DNA, used to treat food
    • Microwaves work on water (heats the molecules in food.
  19. Ultraviolet Light
    • Damages DNA and proteins
    • Cross-linking between G/C and A/T'sĀ 
    • Breaks Disulfide Bridges
    • Bacteria's repair enzymes can be problematic