Nutrition 2

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  1. pH Requirements
    • • Majority of microorganisms grow at a pH
    • between 6 and 8
  2. pH Requirements 2
    •Obligate acidophiles – grow at extreme acid pH

    •Alkalinophiles – grow at extreme alkaline pH
  3. Effects of Osmotic Pressure
    •Dissolved solutes (salts, sugar) create osmotic pressure

    •Most microbes exist under hypotonic or isotonic conditions
  4. Osmotic Pressure
    •Halophiles – require a high concentration of salt

    •Osmotolerant – do not require high concentration of solute but can tolerate it when it occurs
  5. 1. Do all bacteria need oxygen?

    2. Is oxygen harmful to some organism?
    1. No

    2. Yes
  6. How Oxygen is Detoxified
    1. Superoxide dismutase (SOD)

    2. Catalase

    3. Peroxidase
  7. Superoxide dismutase (SOD)
    –Removes  superoxide (oxygen free radicals)

    –Reaction:   2 O2-• + 2H+ -> H2O2 + O2
  8. Catalase
    removes hydrogen peroxide

    –Catalase reaction:  2 H2O2 -> 2 H2O + O2
  9. Peroxidase
    removes hydrogen peroxide

    –Peroxidase reaction: H2O2 + 2 H+ -> 2 H2O
  10. Categories of Oxygen Requirements
    1)Obligate (strict) aerobe – cannot grow without oxygen

    1)Obligate (strict) anaerobe – cannot grow with oxygen

    • 1)Facultative (Facultative anaerobe) –
    • utilizes oxygen but can also grow without it
  11. Aerotolerant anaerobe
    does not utilize oxygen but can survive and grow in its presence
  12. Microaerophile
    requires small amount of oxygen
  13. Providing Appropriate Oxygen Conditions
    •Increased carbon dioxide

    •Carbon dioxide incubators

    –controls CO2 levels

    –similar to conditions of human body

    •Candle jar

    –has increased CO2 levels

    •Reducing Media

    •Both used to growth pathogenic organisms
  14. Cultivation of Anaerobes
    • •Anaerobic growth chamber
    • –Hydrogen combines with oxygen

    • •Anaerobic incubator
    • –oxygen
    • is replaced with N2 gas

    • •Anaerobic media
    • –Thioglycollate broth

    2H2 + O2 -> 2H2O
  15. Cultivation of Microaerophiles
    • •Candle Jar
    • –Burning candle uses O2 and produces CO2

    •CO2 incubator
  16. Nutritional Factors Affecting Microbial Growth
    Carbon, Nitrogen, & Energy Sources
  17. Main determinants of nutritional type
    –carbon source – heterotroph, autotroph

    –energy source – 

    •chemotroph –gain energy from chemical compounds

    •phototrophs – gain energy through photosynthesis
  18. Sources of Essential Nutrients
    Carbon sources


  19. Heterotroph
    • •must obtain carbon in an organic form made by other living organisms such as
    • proteins, carbohydrates, lipids and nucleic acids
  20. Autotroph
    •an organism that uses CO2, an inorganic gas as its carbon source

    • –not nutritionally dependent on other
    • living things
  21. Nitrogen Sources
    •Needed for amino acids and nucleotides

    •Obtained from:

    • –proteins
    • –ammonium ions (NH4+)
    • –nitrites (NO3-)
  22. Nitrogen-fixing bacteria
    –obtain N from N2 in atmosphere
  23. Trace Elements
    •Needed in very small amounts

    •Most serve as cofactors for enzymes


    –Iron (Fe)

    –Copper (Cu)

    –Zinc (Zn)

    –Magnesium (Mg)
  24. Organic Growth Factors
    •Must be obtained from the environment

    •Compounds required for growth


    • –Vitamins
    • –Amino Acids

    • •Fastidious bacteria – require many growth
    • factors
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Nutrition 2
2015-03-14 17:10:08

Nutrition 2
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