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Unit 6--Microbiology

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Unit 6--Microbiology Chapter 19 continued – PowerPoint PPT presentation

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Title: Unit 6--Microbiology


1
Unit 6--Microbiology
  • Chapter 19
  • continued

2
Microorganisms You
  • A. Competition
  • Food for heterotrophs typically are carbon-based
    macromolecules
  • Carbohydrates, lipids, proteins
  • Bacteria fungus are responsible for food
    spoilage because many are saprobes

3
B. Food Microorganisms 1) Making cheese
  • Bacteria placed in an anaerobic environment, and
    the milk breaks down to form cheese
  • Milk (sugar source) little oxygen -gt lactic
    acid protein solids curds

4
2) Making cured meats
  • Some bacteria are able to ferment meat products
  • The final products are sausages, bologna, salami,
    country cured hams, etc

5
3) Making spirits
  • Some fungus (yeast) are able to ferment fruit
    juices to produce alcoholic beverages
  • The final products are wine (from grapes),
  • Sake (from rice), vodka (from potato), beer (from
    grains), etc

6
4) Making breads
  • Some fungus (yeast) ferment plant starches
    producing alcohol CO2
  • The CO2 is trapped within the flour mixture,
    causing the dough to rise
  • While the alcohol is burned off when baking

7
5) Making pickled vegetables
  • For example, sauerkraut is a product of lactic
    acid fermentation of cabbage by the lactobacillus
    bacterium
  • Salt is added to prevent bacteria from spoiling
    the product

8
How else are bacteria helpful?
  • C. Nitrogen-fixation
  • decomposing bacteria convert atmospheric N2 for
    use by autotrophs

9
  • D. Symbiotic bacteria allow a host to live a
    different lifestyle than would normally be
    possible

10
  • E. Cyanobacteria ( unicellular algae) produce
    most of the worlds oxygen by photosynthesis

11
F. Microorganisms your health
Antibiotics that kill pathogenic microorganisms
are made from microorganisms
12
Using sterile plates with aseptic techniques
  • Aseptic
  • sterile or free of microorganisms
  • pathogenic
  • disease-causing
  • purpose to avoid contaminating cultures with
    unwanted species prevent self-infection. Even
    safe or nonpathogenic bacteria can be harmful
    in large amounts or in the wrong place (such as
    the eyes)

13
Aseptic techniques
  • Streaking do not tear the agar application can
    be done with inoculating loops or cotton-tips
  • Sterilization is a must! Use bleach or
  • flaming
  • heat loops in flame until it glows orange
  • pass open lips of test tubes through flame
    several times (after removing before replacing
    stoppers)

14
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16
Filter paper disks (for sensitivity tests)
  • Soak filter paper disks in different bactericides
  • one should be in sterile water as a control
  • place on agar plate which already contains
    bacteria
  • incubate (as needed24 to 72 hours)
  • bacteria grows uniformly wherever their growth is
    not inhibited by bactericide
  • zone of inhibition (halo) where no growth
    occurs the larger the halo, the more
    effective the bactericide

17
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18
Assignment
  • Mark off the bottom of petri plate into 4
    sections. Put a small number (1-4) on outside
    edge of each section.
  • Use a Q-tip to gather specimens from around the D
    hall. Bring your samples back to class for
    streaking on one section of disk (remember your
    number group letter.)
  • Use sterile forceps to apply paper disk, coated
    with antibacterial soap to your section of the
    plate. (Seal with Parafilm incubate.)
  • 48 (?) hours later examine appearance of
    colonies. Note color, texture,etc. Also look
    for other non-bacterial growth, such as molds.

19
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