5-2 Oxidation-Fermentation Test

What are the results of the Oxidative Fermentation test?

- Left: no fermentation of sugar - Left center: slight oxidation of sugar -Right center: fermentation of sugar - Right: oxidation of sugar

What is the purpose of this exercise?

- To determine whether MO's have the ability to oxidize and/or ferment a sugar to acid - To differentiate between the fermentative Enterobacteriaceae (family) and the oxidative Pseudomonas (genus) species

What is the test indicator in the OF test?

Bromthymol blue -- pH indicator

What type of test is this?

Differential -- differentiates bacteria on the basis of fermentative or oxidative metabolism of carbohydrates

What metabolic processes are occurring in the oxidation test?

ETC and Kreb's cycle

A positive F tube indicates that the MO can _____________ ?

Ferment sugars to acid via glycolysis

E. coli can perform?

Fermentation & Oxidation

The color of the test medium in this exercise is ______________ when it is inoculated?

Green

The name of the test medium is _____________?

Hugh and Leifson's OF Medium

A positive O tube and a positive F tube shows that the MO is able to conduct both ________ & ________

Oxidation & Fermentation

P. aeruginosa can perform?

Oxidation only

A positive O tube indicates that the MO is able to ___________ ?

Oxidize a sugar to acid

What is Fermentation?

Sugars are converted to pyretic acid, via Glycolysis, and then broken down into a number of different acids

What is oxidation?

Sugars are oxidized directly to pyretic acid, which can be converted to CO2 and energy via Krebs cycle and Electron Transport

What is a positive indicator for this test?

The semi solid becomes yellow

What is a negative indicator for this test?

The semi solid stays green

What is the purpose of using sterile mineral oil in the OF test?

To create an anaerobic environment for fermentation to occur

Why must two tubes be inoculated per MO in the OF test?

To differentiate between two MO's

Why is sterile mineral oil added to only one tube in the OF test?

To test oxidative or fermentative abilities

At what pH does the test indicator in the OF turn positive?

pH of 6.0 (yellow)

At what pH does the test indicator in the OF turn negative?

pH of 7.1 (green)