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BIOL 351 Lab Practical - Selective Media and Differential Tests

Eugon Agar Deeps
Purpose: Aerotolerance

- Prepared with Tryptic Soy Agar using 10mL instead of the customary 7mL to ensure that the bottom portion is anaerobic.
Anaerobic Jar
Purpose: A means of cultivating anaerobic and microaerophilic bacteria.

GasPak system
- Envelop containing sodium borohydride and sodium bicarbonate
- Paper indicator strip saturated with Methylene blue. Methylene blue is colorless when reduced and blue when oxidized.
- Palladium, which will act as a catalyst to convert H2 and O2 to water.
Mannitol Salts Agar
Purpose: Isolation and differentiation of Staphylococcus aureus.

The Agar:
Phenol red - pH indicator. Yellow below 6.8, red at 7.4 to 8.4, and pink at 8.4 and above.
Mannitol - substrate for fermentation (makes medium differential).
Sodium chloride - High concentration of salt (makes medium selective). Kills most bacteria, but Staphylococci can thrive here.
Mannitol Salts Agar Demo
Staphylococcus aureus (+): growth and color change to yellow
Escherichia coli, Staphylococcus epidermidis, Klebsiella oxytoca, sporosarcina ureae (-): no color change
MacConkey Agar
MacConkey Agar Demo
Escherichia coli and Klebsiella oxytoca (+): growth and red colored
Staphylococcus aureus, Staphylococcus epidermidis, Sporosarcina ureae (-): no growth, not really any color
Methyl Red and Voges-Proskauer Test
Methyl Red and Voges-Proskauer Demo
Methyl Red:
Escherichia coli (+)
Enterobacter aerogenes (-)

Enterobacter aerogenes (+)
Escherichia coli (-)
Catalase Test
Catalase Test Demo
Oxidase Test
Oxidase Test Demo
Nitrate Reduction Test
Nitrate Reduction Test Demo
Micrococcus luteus
Escherichia coli
Soil: bubble present
Citrate Test
Citrate Test Demo
Enterobacter aerogenes (+)
Escherichia coli (-)
Starch Hydrolysis
Starch Hydrolysis Demo
Bacillus subtilis (+)
Escherichia coli (-)
Urea Hydrolysis
Urea Hydrolysis Demo
Proteus vulgaris (+)
Escherichia coli (-)
Indole Test
Indole Test Demo
Escherichia coli (+)
Enterobacter aerogenes (-)
Litmus Milk Medium
Litmus Milk Test Demo
Acid - litmus color change (light blue to pink)

Alkaline - litmus color change (light blue to darker blue): Alcaligenes faecalis

Litmus reduction - light blue to white

Curd - change from fluid to solid: Escherichia coli

Proteolysis - decrease in turbidity of milk (clearer, amber-colored fluid, watery): Proteus vulgaris
Bacitracin Susceptibility Test
Bacitracin Susceptibility Demo
Micrococcus luteus (+): susceptible
Staphylococcus epidermidis (-): resistant
Blood Agar
Blood Agar Demo
Staphylococcus aureus (+): beta
Staphylococcus epidermidis (-): gamma
Coagulase Test
Coagulase Test Demo
Staphylococcus aureus (+)
Staphylococcus epidermidis (-)
Motility Test
Motility Test Demo
Proteus vulgaris (+)
Staphylococcus epidermidis (-)