Growth Media and Parameters

Complex Media

• Made from complex and rich ingredients– 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• 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

5

• Allows the discrimination of different species

• Often contain pH indicators– Allows the discrimination of different metabolisms

Production of acid products turns the medium yellow

Production of alkaline products turns the medium red

Nutrition

• Macronutrients – C,H,N,O,P,S

Carbon

• Required for the synthesis of all organic compounds :– Carbohydrates– Lipids– Proteins– Nucleic acids

• Organic– Monosaccharides

– Disaccharides

– Polysaccharides

– Proteins

– Lipids

– Nucleic acids

– Phenols, Etc.

• Inorganic– CO2

– CO

Carbon Sources

Phosphorous

• Required for the synthesis of :– 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!!– 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

• Autotrophs photolithotrophs• Heterotrophs photoorganotrophes• Autotrophs chemolithotrophs• Heterotrophs chemoorganotrophs

What you have to know about the media

• 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

• 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

• Sources of C,H,N,O,P,S?• Type of media?• Indicators?• Selective agents?• Allow growth of what

bacteria?• Possible reactions?

Environmental Parameters

• Oxygen availability• pH• Temperature

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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