Microbio Lab 3

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4 types of Media

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1. Supportive media - support growth of most clinical organisms
2. Differential media - has substances that are metabolized by some organisms and not by others. Indicators (such as color differences) help you differentiate.
3. Selective media - Has agents which inhibit certain types of organisms while allowing others to grow.
4. Enrichment media - Usually broth based media that suppress the growth of normal flora and encourage growth of pathogenic flora.

Front 2

Basic Ingredients

Back 2

-nitrogen source
-carbon source
-electrolytes
-phosphorus
-indicators

Front 3

Examples of selective agents

Back 3

crystal violet, sodium chloride, phenylethyl alcohol, pH extemes

Front 4

Miscellaneous ingredients

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Agar, Antimicrobial agents, Reducing agents, Blood, Trypticase

Front 5

Selective Media

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-MacConkey, has lactose 1%, fermentor colonies = red, nonfermentor = transparent
-Eosin Methylene Blue, some gram positives may grow. uninoculated media is purplish orange.
-Mannitol Salt, Mannitol positive colonies are yellow, inhibits most bacteria except staphylococcus

Front 6

Catalase

Back 6

Hydrogen peroxide is produced during aerobic respiration. Organisms with catalase will degrade the hydrogen peroxide easily into oxygen and water.

Front 7

Superoxide dismutase

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-the enzyme that degrades the especially toxic superoxide radical formed in aerobic organisms.

Front 8

Testing for Catalase

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drop hydrogen peroxide on an incubated culture. If oxygen bubbles pop up, hydrogen peroxide is being converted by catalase to water and oxygen. This indicates presence of catalase.

Front 9

Testing for cytochrome oxidase

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cytochrome oxidase, by the way, plays a vital role in the electron transport chain.
- Test done by adding a reagent called p-amino... oxalate. this reagent will be oxidized if oxidase is present. this reagent will turn dark if oxidized.

Front 10

Examples of Indicators

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1. Acid-Base indicators: these change colors with pH changes
2. Oxidation-Reduction indicators:

Front 11

Examples of Selective Agents

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1. Crystal Violet: inhibits Gram positive cocci
2. Sodium Chloride: inhibits many types of bacteria
3. Phenylethyl alcohol: inhibits Gram negative bacteria
4. pH extremes: acidic: yeasts and pathogenic fungi, basic: cholerae