MICROBIAL NUTRITION

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• MICROBIAL NUTRITION

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• All living organisms require nutrients
• Micronutrients
• Macronutrients

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How organisms acquire food

• Photoautotrophs use CO2 and sunlight energy
• Photoheterotrophs use sunlight and C in an
  organic form
• Chemoautotrophs use chemical energy from
  reactions
• Chemoheterotrophs use energy from autotrophs or
  other heterotrophs

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Nitrogen

• Makes up 79 of atmosphere
• Most organisms cannot use gaseous nitrogen so
  they are dependent on organisms that can fix
  nitrogen

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Bacterial nutrition

• Different species of bacteria can differ in the
  nutrients that are required
• Some bacteria are picky or fastidious

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• ECOLOGY

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Microbes ( other organisms) are influenced by

• 1. limited resources (e.g., food or nutrients)
• 2. intraspecific interactions
• 3. interspecific interactions
• 4. abiotic factors such as temperature, pH,
  salinity etc.

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• ENVIRONMENTAL FACTORS

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• A. In general, organisms including microbes are
  influenced by
• 1. limited resources (e.g., food or nutrients)
• 2. intraspecific interactions
• 3. interspecific interactions
• 4. abiotic factors such as temperature, pH,
  salinity etc.

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• Graphs will be drawn on the board

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Quantifying Bacteria

• Methods include but are not limited to
• a. Measuring turbidity (cloudiness) in a liquid
  culture.
• (1) an increase in turbidity indicates an
  increase in the number of bacterial cells
  present. We can qualitatively estimate bacterial
  numbers by looking at the degree of turbidity.
• (2) spectrophotometric methods . We can use a
  spectrophotometer to measure the amount of light
  absorbed by a tube containing broth and bacteria
  (or the amount of light that is transmitted).
  This absorbence (or transmittance) can be
  compared to a standard.
• b. Colony counts. Bacteria are plated on agar
  and then the number of colonies that are present
  are counted. If necessary the solution
  containing the bacteria is diluted prior to
  plating by serial dilution
• c. Cell counts
• (1) microscopic - the number of bacterial cells
  in a sample is counted
• (2) Coulter method - a machine determines the
  number of cells that are present in a sample

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• How to maintain microbes in the laboratory

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Types (physical) of media

• a. liquid (e.g., broth)
• b. semisolid with a gelatinous consistency
• c. solid or firm containing agar (a solidifying
  agent, a complex polysaccharide derived from red
  algae).

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• Properties of agar
• (1) solid at room temperature
• (2) liquid at the boiling point of water (100oC)
• (3) resolidifies at 42oC
• (4) because of this, agar can be melted (and
  sterilized) and then poured into individual petri
  dishes. Prior to the inoculation of microbes
  media must be sterilized.

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Functional types of media

• a. general purpose media for the growth of many
  different species of microbes
• b. enriched (AKA Complex) media contain extra
  ingredients e.g., blood,
• c. selective and differential media are designed
  for the growth of certain bacterial species. A
  selective medium contains one or more agents that
  inhibit the growth of certain species while not
  inhibiting the growth of other species. Thus the
  latter is selected for. A differential medium
  supports the growth of several species of
  bacteria but these bacterial species appear
  different.
• d. Misc. media such as reducing media that
  reduce the reduction-oxidation potential

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