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Bacterial Growth

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Bacterial Growth I. Determine in terms of population size. Nature there is a of organisms living together. How can we get a certain type of bacteria? – PowerPoint PPT presentation

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Title: Bacterial Growth


1
Bacterial Growth
2
  • 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.

3
  • - 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 -

4
Streak-Plate Method
5
  • 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.

6
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?

7
  • 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.

8
  • 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

9
Review
  • Describe the difference between direct count and
    plate count method.
  • What are the three temperate ranges that
    bacteria tend live in?

10
  • 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.

11
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12
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?

13
  • 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.

14
  • 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).

15
  • 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.

16
  • 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.

17
  • 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 .

18
  • B.
  • C.
  • D.
  • Small organic molecules other than carbon that
    bacteria must provide in order to grow (amino
    acids vitamins).

19
V. Dynamics of population growth.
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