3) Micro Bio Lab Practical (Phenol Red Broth & OF test)

What is the purpose of the phenol red broth?

To determine if bacteria can metabolize a specific carbohydrate

What are peptones used for in phenol red?

Food for general growth

What is NaCl used for in phenol red?

Salt balance

What is the pH indicator in phenol red?

Phenol red: yellow w/ turbidity = acidic (+), red/orange = neutral, magenta/pink = alkaline (-)

Why do phenol red results need to be done between 24-48 hours?

After sugar runs out, bacteria metabolize peptones instead, raising the pH (can lead to a false (-))

What is the purpose of the Oxidation/Fermentation test?

Determine whether bacteria oxidize and/or ferment glucose

Why is a needle used for inoculation in OF test?

To stab agar deep

Why is mineral oil used in one of the tubes during OF test?

To create anaerobic conditions (for bacteria to FERMENT glucose)

What is dipotassium phosphate used for in OF test?

pH buffer

What is the pH indicator in OF test?

Bromothymol blue

yellow = acidic

green = neutral

blue = alkaline

What is glucose used for in OF Test?

Substrate for oxidation or fermentation

What would a (+) result be in the oxidation (aerobic) tube?

Bacteria oxidized w/ oxygen, produced acids

What would a (+) result be in the fermentation (anaerobic) tube?

Bacteria fermented w/out oxygen, produce acids, alcohol, and gas

What is a facultative anaerobe?

Bacteria that grow w/ or w/out oxygen, but better w/

What does non-saccharolytic mean?

Does not use sugar, metabolize peptones aerobically