Thermo Scientific™ OF Medium w/1% Xylose

Description

• Determine oxidative and fermentative metabolism of xylose by gram-negative bacilli using Thermo Scientific™ Remel™ OF Medium w/1% Xylose (Hugh-Liefson)
• Hugh and Leifson first reported that microorganisms which utilize carbohydrates oxidatively produce only a minimal amount of acid 1
• Oxidative-Fermentative (OF) Medium was developed with a ratio of peptone to carbohydrate that minimized the formation of alkaline by-products and enhanced acid production by oxidative organisms
• OF Medium is especially suitable for determining the carbohydrate metabolic pathway of gram-negative bacilli 2
• Typical fermentation media contain approximately 2% peptone and 1% carbohydrate
• In media containing high concentrations of peptones, oxidative microorganisms produce alkaline by-products in quantities that neutralize the acid produced from carbohydrate metabolism
• OF Medium is a semisolid medium with low peptone to carbohydrate ratio that contains the pH indicator bromthymol blue
• Organisms which metabolize carbohydrate in OF medium produce acid in quantities sufficient to prevent its neutralization by alkaline peptone by-products
• Ready to use – Convenience of prepared media Uses 4 mL of 1% xylose as carbohydrate source Easy to interpret – Color change from green to yellow indicates positive test for acid production
• When testing for motility, growth diffused away from stab line of inoculation indicates a positive test whereas growth confined to stab line indicates negative test
• Acid production in the open tube (without mineral oil overlay) indicates oxidative metabolism whereas acid production in both (with and without mineral oil overlay) tubes indicates fermentative metabolism
• OF Medium with Xylose uses 4 mL of 1% xylose as a fermentable carbohydrate
• The medium contains casein peptone as the substrate and bromthymol blue as the pH indicator
• Dipotassium phosphate promotes fermentation and also serves as a buffer
• Agar allows for detection of motility and aids in even distribution of acid produced at the surface of the medium
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• Remel™ and Oxoid™ products are now part of the Thermo Scientific brand.