The objective of the exercise is to determine which organisms can utilize each sugar. Phenol red is a pH indicator which turns yellow below a pH of 6.8 and fuchsia above a pH of 7.4. If the organism is able to utilize the carbohydrate, an acid by-product is created, which turns the media yellow.

What does the phenol red test determine?

The objective of the exercise is to determine which organisms can utilize each sugar. Phenol red is a pH indicator which turns yellow below a pH of 6.8 and fuchsia above a pH of 7.4. If the organism is able to utilize the carbohydrate, an acid by-product is created, which turns the media yellow.

What is the phenol red thread test?

The mice are gently restrained (not anesthetized) and a phenol red loaded thread (Zone-Quick) is placed in the lateral canthus for 20 seconds to measure tear production. The amount of thread that turns red (change in pH from wetting by tears) is measured in millimeters.

What does red mean in phenol red test?

Principle: Phenol Red Fermentation medium contains peptone, phenol red (a pH indicator) and the carbohydrate to be tested. Phenol red is yellow at a pH < 6.8 and red at a pH of > 7.4, therefore if a bacterium ferments a sugar to acid a yellow color will develop.

What is the purpose of the phenol red test quizlet?

Phenol red broths are used to determine if a bacterium can ferment a particular sugar, and if it does ferment, if acid or acid and gas are produced.

What does methyl red test for?

The methyl red test is used to detect the ability of an organism to produce and maintain acid end products from glucose fermentation.

What is phenol red quizlet?

Phenol Red Indicator — shows formation of acids from sugar via change in color due to pH change.

How is tear osmolarity measured?

The most commonly applied technique for measurement of tear osmolarity is through observation of the change in the freezing point of tear samples. The major benefit of this technique is that it requires only microliter samples of tears (∼0.2 μL).

What is the purpose of phenol red in the TSI medium?

TSI Agar contains three sugars (dextrose, lactose and sucrose), phenol red for detecting carbohydrate fermentation and ferrous ammonium sulfate for detection of hydrogen sulfide production (indicated by blackening in the butt of the tube).

What reagent is methyl red test?

Media and Reagents Methyl red-Voges-Proskauer (MR/VP) broth (formulated by Clark and Lubs) is used in this test. Media and reagents can be prepared in house or purchase from commercial providers. Dissolve 0.1 g of MR in 300 ml of ethyl alcohol, 95%.

What is the purpose of the methyl red test quizlet?

The MR test is designed to detect organisms capable of performing mixed acid fermentation, which overcomes the phosphate buffer in the medium and lowers the pH.

Why is my phenol red yellow quizlet?

(B/c phenol red turns YELLOW when ACIDS ARE RELEASED into the medium / when the medium has an acidic pH. Also, a yellow tube indirectly indicates FERMENTATION HAS OCCURRED). INCREASE the pH of the medium, which leads to an ALKALINE pH.