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Growth Media and Parameters
Complex Media
• Made from complex and rich ingredients
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Ex. Soya protein extracts
Milk protein extracts
Blood products
Tomato juice, etc.
• Exact chemical composition unknown
• Can be selective and/or differential
2
Defined Media
• Known chemical composition
May contain up to 80 different ingredients
– May be quite simple
– Allows the growth of a restricted number of
microorganisms
– Highly variable composition as a function of the
microorganism
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• May be selective and/or differential
3
Selective Media
• Contains compounds which inhibit or kill the
unwanted organisms
– Ex. Medium containing penicillin only allows the
growth of penicillin resistant microorganisms
4
Differential Media
• Allows the discrimination of different species
• Often contain pH indicators
– Allows the discrimination of different metabolisms
Production of alkaline
products turns the
medium red
Production of acid
products turns the
medium yellow
5
Nutrition
• Macronutrients
– C,H,N,O,P,S
Carbon
• Required for the synthesis of all organic
compounds :
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Carbohydrates
Lipids
Proteins
Nucleic acids
Carbon Sources
• Organic
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Monosaccharides
Disaccharides
Polysaccharides
Proteins
Lipids
Nucleic acids
Phenols, Etc.
• Inorganic
– CO2
– CO
Phosphorous
• Required for the synthesis of :
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Nucleic acids
Phospholipids
ATP
Used as a buffer; control of pH
• Sources:
– Organic and inorganic
• The inorganic form is the most used
Nitrogen
• Required for the synthesis of:
– Amino acids
– Nucleic acids
– Peptidoglycan
• Sources:
– Organic: Amino acids
– Inorganic: NH3, NO3, & N2
Sulfur
• Required for the synthesis:
– Amino acids (Cysteine/Methionine)
– Vitamins (thiamine and biotin)
• Sources:
– Organic: Amino acids
• Cystein and methionine
– Inorganic:
• S, SO4
Hydrogen and Oxygen
• Required for the synthesis of organics!!
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Carbohydrates
Lipids
Proteins
Nucleic acids
• Sources:
– Organic:
• Organic carbon
– Inorganic:
• H2 (Methanogens only)
Nutritional Classification
• Carbon sources
– Heterotrophs:
• Preformed organic compounds
– Autotrophs:
• Inorganic molecules
– CO2 and CO
Nutritional Classification (Cont’d)
• Energy sources
– Phototrophs:
• Light
– Chemotrophs:
• Oxidation of organic and inorganic compounds
• Source of e– Organotrophs:
• Reduced organic molecules
– Lithotrophs:
• Reduced inorganic molecules
Nutritional Types
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Autotrophs photolithotrophs
Heterotrophs photoorganotrophes
Autotrophs chemolithotrophs
Heterotrophs chemoorganotrophs
What you have to know about the
media
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What are the sources of C,H,N,O,P,S?
What type of media is it?
What are the indicators?
What are the selective agents?
They allow the growth of what bacteria?
What are the possible reactions?
Ex. MacConkey Agar
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Sources of C,H,N,O,P,S?
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Type of media?
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Indicators?
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Selective agents?
Allow growth of what bacteria? •
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• Possible reactions?
Peptone - 17 g
Proteose peptone - 3 g
Lactose - 10 g
Bile salts - 1.5 g
Sodium chloride - 5 g
Neutral red - 0.03 g
Crystal Violet - 0.001 g
Agar - 13.5 g
Environmental Parameters
• Oxygen availability
• pH
• Temperature
18
Oxygen Requirements
• Aerobic:
– Absolute need of oxygen to survive
– Used as a final electron acceptor
– Used by bacteria that carry out an oxidative or
aerobic respiratory metabolism
• Microaerophilic:
– Absolute need for low concentrations of oxygen
– High concentrations are detrimental
Oxygen Requirements (Cont’d)
• Anaerobic/Aerotolerant:
– Oxygen is not required for growth or survival but is
tolerated
• Facultative anaerobes:
– Facultative oxygen requirement
– May use oxygen or not
– Possesses an oxygen dependant and oxygen
independent metabolism
• Strict or obligate anaerobic :
– Oxygen is neither used nor tolerated; cannot survive
in the presence of oxygen