Phenol Red Broth Tests: does the organism ferment sugar?

If given a description of results, know what that means about the organism’s fermentation capabilities with that sugar 

• Yellow result: positive for acid production 

• Red result: no acid is produced therefore negative

If given the details of an organism's fermentation capabilities be able to describe how the results should come out (the specific color of the broth and presence/absence of a bubble in the Durham tube) 

• Yellow broth with bubbles: the organism ferment the sugar to produce acid and gas 

• Yellow broth no bubbles: the organisms ferments the sugar to produce acid but not gas 

• Red broth no bubbles: organisms cannot ferment sugar and no acid or gas is produced from it.

Know what a Durham tube is for 

Capture and trap gas during fermentation 

What is the purpose of performing a Phenol Red test, what does it tell you about an organism? 

Does the organism ferment sugar? 

If an organism has the ability to ferment a certain carbohydrate, what substance is made that changed the color of the media/broth culture

An acid

What is the function of a Durham tube in the phenol red test?

To trap any gases that were produced during fermentation 

Why do we NOT screw the lids to test tubes down all the way and instead leave them a little loose before incubation?

Because gasses will increase the pressure inside the tube 

You inoculate a Phenol Red - SUCROSE test with an unknown organism and incubate it. After incubation you observe the media is red. What does this tell you about the organism 

Negative for fermentation of sucrose

You inoculate a Phenol Red - GLUCOSE test with an unknown organism and incubate it. After incubation you observe a bubble in the Durham tube. What TWO things does this tell you about the organism 

It is positive for glucose fermentation and produce a gas

You inoculate a Phenol Red - LACTOSE test with an organism who is able to ferment lactose, but does not produce gas while doing so. How should the tube look after incubation in terms of color and the Durham tube?

Fluid will be yellow and no bubbles in the Durham tube