Oxidation-Fermentation Test (OF Test 2)
The purpose of this test is to determine whether an organism attacks sugars (in this case glucose is used) by fermentation or oxidation. Two tubes of Hugh & Leifon's medium are used. In one tube the medium is covered with vaseline. If the organism is an oxidizer it will produce acid only in the open tube (without vaseline), if it is a fermenter it will produce acid in the vaseline-covered tube and in the open tube. Some aerobic bacteria may use the peptone in the medium, producing ammonia, with resulting alkalinity (blue) in the top part of the open tube. The indicator used is bromthymol blue. 1. Uninoculated medium. 2 + 3. Oxidative reaction: Pseudomonas fluorescens. 4 + 5. Negative reaction with alkaline reaction in the top part of the open tube: Alcaligenes.
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