Lab Exercise 42 PDF

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Lab Report 42 Name: __Michele Glantz__ Date: ___6/10/19_______

Phenol Red Broth Your Results and Observations Record your results after incubation in the table.

Organism Color S. aureus E. coli P. aeruginosa

Glucose Lactose Glucose Lactose Glucose Lactose

Red Red Yellow Yellow Yellow Red

Results Gas Production No No Yes Yes Yes Yes

Interpretation Alkaline Alkaline Acid and Gas Acid and Gas Acid and Gas Alkaline

Interpretation and Questions 1. Why is this broth made without adding significant amounts of general nutrient extracts? The broth has a combination of sugars. It is testing for both glucose and lactose. More extracts are not necessary. 2. One of your fermentation tubes turned a bright red color and plenty of bacterial growth was evident in the tube. What happened? Why is there no bubble in the Durham tube? The bacteria did not utilize the glucose. The growth may be due to the organism that is being able to use nitrogen for growth. 3. How would you test an organism’s ability to ferment another sugar, such as ribulose? When it comes to this kind of test, I believe the best way of going about it is to utilize a pH indicator in order to show acid production due to the fact that ribose produces acid during fermentation. 4. You are doing sugar fermentation tests. How would you determine that fermentation occurred? You can determine if fermentation occurred if the broth turns into the color yellow. This conveys that the pH has dropped from the acid production. 5. Describe the functions of phenol red, the carbohydrate source, Durham tube, and peptone in phenol red fermentation media. Phenol red is the pH indicator. Carbohydrate source is used for fermentation. The Durham tube is used to trap gas production. Peptone is the differential test medium.

Lab Report 42 6. Why is only a single sugar present in each phenol red tube? Can multiple sugars be tested simultaneously? Why or why not? Only one sugar is present because it tests the ability to use that sugar. More than one sugar being used would not allow for the differentiation between what sugars are being used....