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MICROBIAL NUTRITION
I.
Nutrition
A.
Microorganisms obtain:
All substances required for synthesis of cellular material from the
environment
B.
Nutrients:
Substances necessary for microbial:
Maintenance
Growth
Reproduction
Used in biosynthesis & generation of energy
Must be available in a usable chemical form
C.
Macronutrients:
Major elements required in large amounts (Grams/liter):
Carbon
Hydrogen
Nitrogen
Oxygen
Phosphorous
Sulfur
Components of:
Lipids
Carbohydrates
Proteins
Nucleic acids
Minor elements required in mg amounts/liter:
Potassium
Calcium
Magnesium
Iron
Components of:
Enzymes
Coenzymes
Cytochromes
D.
Micronutrients - essential for life but required in small amounts
Trace elements - required in g amounts/liter
Manganese
Zinc
Cobalt
Molybdenum
Nickel
Copper
Components of enzymes & co-factors, aid in maintenance of protein
structure
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II.
E.
Growth factors:
Small organic molecules that the organism requires but can not make
(required in g amounts/liter):
Essential amino acids
Vitamins
Purines & Pyrimidines
F.
Requirements for Carbon, Hydrogen, & Oxygen often satisfied together:
Carbon containing molecules usually contain O & H
Exceptions:
CO2 (oxidized & lacks H)
All microorganisms can reduce & incorporate CO2 into
organic molecules.
AUTOTROPHS:
A.
Use CO2 as their sole carbon source:
B.
Obtain energy from light or inorganic compounds
Phototrophs use light:
Contain chlorophyll:
Plants
Algae
Green bacteria
Purple bacteria
Blue-green bacteria
C.
D.
III.
Lithotrophs (rock-eaters) use reduced inorganic compounds as electron /
hydrogen (energy) sources:
Certain bacteria
However, reduction of CO2 requires a great deal of energy:
Many microorganisms cannot use CO2 as their sole carbon source
HETEROTROPHS:
A.
Require an organic compound as a source of carbon
B.
Organic compounds include:
Carbohydrates:
Starch
Glycogen
Cellulose
Sugars
Lipids
Proteins
C.
Also require an organic energy source
D.
Heterotrophic organisms include:
Animals
Fungi
Most protozoa
Most bacteria
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IV.
E.
Nutritional requirements vary among species:
Range from simple (salts, an organic carbon & energy source) to
extremely complex.
F.
Mutations may change nutritional requirements:
Prototroph:
Microorganism requiring the same nutrients as most of the
naturally occurring members of its species
Auxotroph:
Mutated prototroph which lacks the ability to synthesize an
essential nutrient & must obtain it from its environment
Culture media
A.
Specialized media have been developed in which to grow bacteria:
B.
Two principle types:
1.
Defined media:
Contains known amounts of chemically defined substances
2.
C.
Complex media:
Contains known amounts of substances which have not been
chemically defined:
Peptone(Protein hydrolysate)
Supply amino acids
Extracts:
Animals
Plants
Soil
Supply:
Carbon
Energy sources
Salts
Elements
Growth factors
Types of culture media
1.
General purpose media:
Support growth of many microorganisms
2.
Enriched media:
Special nutrients added to support growth of fastidious
heterotrophs
3.
Selective media:
Favor growth of particular microorganisms
4.
Differential Media:
distinguish between different groups of bacteria & permit tentative
identification on the basis of biological characteristics
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