Chapter 6 Microbial Nutrition and Growth

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Chapter 6 Microbial Nutrition and Growth

• Requirements for growth
• Chemical
• Physical
• Pure bacterial cultures
• Cultivating prokaryotes in the lab
• Principles of bacterial growth
• Methods to detect and measure growth

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Chemical Requirements Nutrition

• organic carbon as
  carbon source
• inorganic (CO2) as
  carbon source
• All org. require other major elements and trace
  elements
• Trace elements Cobalt, zinc, copper, maganese,
  etc.
• Some species require growth factors

Major Elements
Functions
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Chemical Requirements Nutritional Diversity
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Chemical Requirements Oxygen

• O2 derivatives can be toxic
• Singlet oxygen (1O2) ? detoxified by superoxide
  dismutase ?
• Peroxide anion (O22-) from H2O2 ?
• Superoxide radical (O2-)
• Hydroxyl radical (OH) from IR or incomplete
  H2O2 detoxification

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Physical Requirements Effects of Temperature on
Growth
Optimum growth temperature
5ºC
25ºC
35ºC
Figure 6.4
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Physical Requirements Temperature
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Extremophiles
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Physical Requirements pH

• pH optimum
• Cells maintain pH 7.2 no matter environmental pH
• Ex. Escherichia coli neutrophile found in human
  colon
• Ex. Thiobacillus ferroxidans lives at pH 2,
  oxidizes sulfur, pumps out H
• Ex. Bacillus alcalophilus lives at pH 10.5,
  exchanges Na for H

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Physical Requirements Water

• High solute concentration makes water unavailable
  to cells
• cell dehydrates,
  shrinks away from cell well
• Cells can increase intracellular solute
  concentration
• 
  Staphylococcus
• Archea
  Great Salt Lake, Dead Sea

Plasmolysis
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Ecological Associations

• Symbiotic relationships
• Metabolic
  wastes of species may serve as nutrients of
  another species
• Many bacteria live on
  polysaccharide-encased microbe community
• Quorum sensing ?
• Organized architecture with channels for
  nutrients and waste
• Protect organisms against disinfectants and
  antimicrobials
• Biofilms useful in
• Formation of biofilms can facilitate disease
• Dental plaque
• Salmonella enterica, Staphylococcus aureus,
  Pseudomonas aeruginosa

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Flow of solute through a biofilm
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Pure Bacterial Cultures

• In the lab bacteria are isolated and grown in
• Cultures may be from environmental specimens or
  clinical specimens
• All glassware, media and instruments must be
  sterile prior to use ?
• can be maintained
  on solid, slant agar at 4º C or in glycerol
  solution at -70º C

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Clinical Sampling
Table 6.3
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Isolation Streak Plate MethodGoal
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Isolation Pour Plate Method
Figure 6.9
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Catagories of media used to grow bacteria

• Contains peptones, extracts and many nutrients
• Contains precise mix of pure chemicals
• Contains ingredients which will favor growth of
  particular organism or inhibit growth of all but
  particular organism
• Contains ingredient that can be changed by
  bacteria in recognizable way

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Representative Types of Agar Media