Bacterial Growth

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Bacterial Growth
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• I. Determine in terms of population size.
• Nature there is a of organisms
  living together.
• How can we get a certain type of bacteria?
• - separating the progeny of a
  single bacterium from all others.

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• - interested in disease
  causing bacteria (major contributor to pure
  culture techniques).
• Initially grew bacteria on potato surface but
  had problem
• Not enough for bacterial
  growth.
• Added gelatin as a solidifying agent. (Warm -
  pour, cool - solid)
• -
  simplest most common method to isolate a
  single bacterium.
• Hesse (Kochs assistant)
  (polysaccharide extract from marine algae) -
  easier to work with then gelatin (solid over a
  wider range then gelatin).
• Julius Petri -

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Streak-Plate Method
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• II. Bacterial growth
• formula to determine population size
• b B2n
• Number of cells at time zero (beginning).
• number a cells at any later time.
• number of cell generations.

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Review

• Why is agar used instead of gelatin or potato?
• Why is the petri dish unique to prevent
  contamination?
• What is the advantage of bacterial growing by
  binary fission? What is the disadvantage?
• How many bacteria will there be after 10 hours if
  the bacteria double every 30 m inutes?

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• A. Growth can be measured as an increase in
  (weight) of the population.
• B. Growth can be measured as an increase in
  .
• 1. - count the
  number of colonies on the medium.
• 2.
  - counting the number of
  bacterium in an known volume of liquid.

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• III. Factors that influence microbial growth.
• A. Temperature
• 1. Most bacteria grow within or near
  .
• 2. groups of bacteria based
  upon their optimum growth temperatures.
• a. 5C - 20C
• b. 20C - 50C
• c. 50C - 80C
• d. 80C

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Review

• Describe the difference between direct count and
  plate count method.
• What are the three temperate ranges that
  bacteria tend live in?

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• 3. Food Preservation
• Refrigerators food spoilage
  because most of the microorganism that cause
  spoilage are .
• 4. Temperature Human diseases.
• Human body
• 37C (
  ).
• 20C - 25C (
  ).
• Ex - leprosy (Mycobacterium leprae)-
  involves the regions of the
  body.

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Review

• Why do we store our food in refrigerators?
• Why do you not want to keep heating and cooling
  the same leftover throughout the week?
• Which temperature range to most tend to live in
  and why?

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• B. Oxygen Requirements
• 1. -
  require free oxygen to grow.
• 2. - will
  not grow in the presence of free oxygen, may even
  be killed.
• 3.
  -prefers the presence of low oxygen (2 - 10
  Oxygen).
• 4.
  - lives in the presence of
  both
• Growth occurs more rapidly in the presence of
  oxygen.
• 5.
  - will grow in the presence of oxygen but do
  not posse an oxidative metabolism
• Derive no benefit from the presence of oxygen.

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• Why can some bacteria thrive in the presence of
  oxygen but others are killed by it?
• Oxygen can be converted into a toxic form like
  (H2O2)
  (O2-).
• Cells that do not die in the presence of oxygen
  produce enzymes ( ) into a form (H20
  O2).

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• C. pH
• Most bacteria grow best in an medium with a pH
  of (neutral).
• Can live in a wider range
• Ex. Helicobacter pylori - live in very
  environments ( )
  may cause ulcers.
• Bacteria produce metabolic products that may
  acidic or basic.
• Need a ( ) to
  grow bacteria.

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• 4. - pressure that is
  required to prevent the net flow of water across
  the cell membrane.
• effect
  water movement.
• Use salt as an factor
  in food preservation.

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• IV Cell multiplication requires a source of
  energy raw material for synthesis of cell
  components.
• A. Bacterial Nutrients
• Raw Materials
• Carbon, Nitrogen, Oxygen, Hydrogen.
• all other compounds including ions.
• Two Purposes of nutrition
• 1. (Synthesize) protoplasm.
• 2. Supply energy to .

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• B.
• C.
• D.
• Small organic molecules other than carbon that
  bacteria must provide in order to grow (amino
  acids vitamins).

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V. Dynamics of population growth.