Bacterial Growth

1
Bacterial Growth

• Growth Requirements
• Environmental Effects

2
Bacterial Growth Characteristics

• Culture Media
• Chemicals
• Carbon
• Nitrogen
• Micronutrients (S, P, Fe, Mg, K, Na, etc.)
• Solid or Liquid
• Agar for solid support
• Sterilization usually using an autoclave

3
Bacterial Growth Characteristics

• Agar
• Extract of seaweed (red algae) a polysaccharide
  of galactose and galacturonic acid
• In 1881, Fannie Hesse, who was working as a
  technician for her husband in the laboratory of
  Robert Koch, suggested agar
• Used as setting agent in jam making for some time
  
• Replaced gelatin (poor temperature
  characteristics and supports growth)
• Dissolves at 90C and solidifies at 40C

4
Bacterial Growth Characteristics

• Culture Media
• Selective and Differential Media
• Complex vs. chemically defined

5
Bacterial Growth Characteristics

• Selective and Differential Media
• Differential - differentiates between organisms
  based upon colony morphology (especially color)
  on media
• Selective - permits only certain organisms to
  grow (e.g. high salt or other inhibitors)

6
Bacterial Growth Characteristics

• Complex vs. chemically defined
• Chemically defined each component has a know
  chemical formula and/or structure, e.g. minimal
  media (glucose, ammonium nitrate, and a defined
  mixture of salts)
• Complex media (undefined) components come from
  non defined sources, e.g. tryptone, peptone,
  yeast extract, oatmeal

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Bacterial Growth/Environmental

• Energy sources
• Carbon sources
• Physical influences on growth

8
Bacterial Growth/Environmental

• Energy sources
• Organisms acquire energy as a result of
  oxidation/reduction reactions
• Light energy - phototroph
• Chemical energy - chemotroph
• organic (reduced forms of carbon)
• inorganic (reduced metals)

9
Bacterial Growth/Environmental

• Carbon sources
• autotrophs use carbon dioxide
• heterotrophs use reduced organic carbon sources
• sugars
• organic acids
• alcohols

10
Bacterial Growth/Environmental

• Nitrogen sources
• Reduced (ammonia)
• Nitrates and Nitrites
• Nitrogen Fixation

11
Bacterial Growth/Environmental

• Nutritional Classifications - based upon energy
  carbon source
• photoautotroph - uses light energy and carbon
  dioxide as carbon source
• photoheterotroph - uses light energy and an
  organic carbon source
• chemoautotroph - uses an inorganic chemical as
  energy and carbon dioxide
• chemoheterotroph - uses an organic chemical as
  energy and an organic carbon source

12
Bacterial Growth - Physical

• Physical Influences on Growth
• Temperature
• pH
• Osmotic pressure
• Oxygen availability
• Oxygen toxicity

13
Bacterial Growth - Physical

• Temperature
• psychrophillic - an organism that exhibits
  optimal growth at about 15 deg. C and does not
  grow above 20 deg. C
• mesophillic - an organism that exhibits optimal
  growth at about 30-37 deg. C and does not grow
  below 10 or above 50 deg. C
• thermophillic - an organism that exhibits optimal
  growth between 50-60 deg. C and does not grow
  below 40 deg. C or above 70 deg. C
• Hyperthermophillic growth between 70 and 110
  deg C

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Bacterial Growth - Physical

• pH
• most bacterial prefer pH 7 or slightly acidic
• can tolerate to pH 4 due to production of organic
  acids during glucose metabolism

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Bacterial Growth - Physical

• Osmotic Pressure
• ideal seems to be about 0.5 to 1.0 NaCl
• some organisms tolerate much higher salt, e.g.
  Staphylococcus will go to 10 NaCl
• halophiles - adapted to high salt concentrations
  many belong to Archea bacteria

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Bacterial Growth - Physical

• Toxic Oxygen - Forms
• Singlet oxygen
• Superoxide free radicals
• Peroxides
• Hydroxyl free radicals

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Bacterial Growth - Physical

• Toxic Oxygen - Neutralization
• Catalase
• 2 H2O2 ? 2 H2O O2
• Superoxide dismutase
• 2 O2 - 2 H ? O2 H2O2
• Peroxidases
• H2O2 ? H H2O

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Bacterial Growth - Physical

• Oxygen Classification
• Aerobic - grows in presence of oxygen
• Obligate aerobe - requires oxygen
• Anaerobic - grows in absence of oxygen
• Obligate anaerobe - will only grow in absence of
  oxygen
• Facultative anaerobe - will grow both
  anaerobically or aerobically

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Bacterial Growth - Physical

• Oxygen Classification
• Aerotolerant - only grow anaerobically but will
  tolerate oxygen
• Microaerophillic - growth occurs only in presence
  of low concentrations of oxygen

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Bacterial Growth - Physical