Mod 8 & Expansion Module

The ability or inability of a particular species to ferment a particular carbohydrate depends on the presence or absence of an enzyme system to convert that carb to glucose. Those that can ferment - have a variety of by products ( ex. acids, liguid, gases.) All bacteria that fermetn carbs the by product is always acid.

• 1. Carbohydrates: contatin single carb.
• 2. Phenol Red: A pH indicator; yeloww -pH below 6.8, red - pH 6.8-7.4, pink -above pH7.4
• 3. Durhan Tube: produced gasses get trapped in this upside down tube.

The result may be different everytime you run a test because bacteria doesnt' always give the same results. With single test - cannot absorve "v"

• if bacteria can reduce sulfur to hydrogen sulfide it will be visible as black precipitate.
• if bacteria ferments only glucose after 18hr the tube will be red and butt yellow.
• If glucose and lactose, or gulocse ans sucrose are fermented the enitre tube turn yellow
• if gas produced - cracked agar.

• + test = cloud, diffuse growth throughout the medium
• - test = well defined growth alon the stab only.

• to identify organisms tha produce the enzyme catalase.
• If catalase present, the added hydrogen peroxyde will be converted into water and O2 which escapes as a gas.