Microorganisms and Their Environment

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Microorganisms and Their Environment

• October 11, 2004

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What are Microorganisms?

• A microorganism is any living thing of
  microscopic size or smaller.
• Bacteria Yeasts Protists

40,000x Mag. 10,000x Mag. 200x
Mag. Also Viruses, some Algae, and some Animals
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The Importanceof Microorganisms

• Microorganisms have positive and negative
  effects on humanity.
• Many foods, beverages, and medicines are made
  with the help of bacteria and yeast.
• The spoilage of food and many diseases are
  caused by microorganisms.

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The Benefits of Microorganisms

• Beer made with yeast.
• Bread made with yeast.
• Champagne made with yeast.
• Cheese made with bacteria.
• Pickles made with bacteria.
• Sauerkraut made with bacteria.
• Soy Sauce made with bacteria.
• Yogurt made with bacteria.

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The Drawbacksof Microorganisms

• Some bacteria cause infections and diseases like
  tuberculosis and bubonic plague.
• Some protists cause diseases like malaria and
  sleeping sickness.
• Some viruses cause diseases like the flu,
  measles, chicken pox, polio, and HIV.
• Some yeasts also cause infections.

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An Experimental Question

• What conditions are suitable for growing
  microorganisms for our benefit?
• Or
• What conditions are necessary to prevent the
  growth of microorganisms?

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Our Experimental Organism

• Bakers Yeast (S. cerevisiae) is found
  naturally growing on grapes and other fruits.
• It has been used for thousands of years for
  baking and brewing.

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Characteristics of Bakers Yeast

• Readily available in the grocery store.
• Can grow in temperatures ranging from 8 to 40
  degrees C. (46 to 104 degrees F.)
• Can survive pH levels between 2.4 and 7.4
• Reproduces quickly, optimally doubling every
  hour.

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Metabolism of Bakers Yeast

• In the absence of oxygen, yeast will undergo
  anaerobic respiration.
• C6H12O6 ? 2 C2H6O 2 CO2
• Glucose Ethanol Carbon
• Dioxide
• Yeast can also use sucrose (cane sugar) and
  fructose (fruit sugar) as a sugar source.

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Characteristics of Various Liquids
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Independent (Input) Variables

• What conditions should we test in our
  experiment?
• We will grow our yeast in liquid to easily
  deliver the sugar source.
• But what liquids should we pick?

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Dependent (Output) Variables

• Remember that we want to determine what
  conditions are most suited to growing yeast
  cells.
• How can we use the reactants and / or the
  products of yeast metabolism to answer our
  experimental question?

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Yeast Incubation Tube
Grape Juice Time 0 hours
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Sealed YeastIncubation Tube
Apple Juice Time 24 hours
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A Pair of Sealed YeastIncubation Tubes
Apple Juice Milk Time 24 hours
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The CompleteExperimental Set-Up
CO2 Collection Tubes Incubation Tubes
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CO2 Collection Tubes
Time 0 hours 0 ml CO2 Collected
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CO2 Collection Tubes
Time 24 hours 1 ml CO2 Collected
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CO2 Collection Tubes
Time 48 hours 5 ml CO2 Collected