Question

Phenal red glucose, lactose, and sucrose fermentation tests are valuable because, select all that apply

a. Helps distinguish species of bacteria that are different, but look the same under the microscope

b. Characterize metabolic strategies of newly discovered bacteria

c. These fermentation tests can identify an organism with no other information

d. Determines which sugars an organism can ferment

I answered d and only got partial credit, need help figuring out the other answers. thanks

Answer 1

Introduction: Phenol red broth is a differential medium commonly used for identification of sugar fermentations as well as to differentiate the bacteria belonging to the family of Enterobacteriaceae. The broth has peptone, a carbohydrate (glucose, lactose or sucrose), phenol red indicator and a Durham tube. An organism ferments sugars to produce pyruvic acid which is an acidic end product that turns phenol red indicator into yellow color and when the organism’s fermentation end product is ammonia which is alkaline, it turns into magenta color. Gas production by the organism is indicated as an air bubble in the Durham tube.

Answer:

Phenol red glucose, lactose, and sucrose fermentation tests are valuable because, select all that apply

a. Helps distinguish species of bacteria that are different, but look the same under the microscope.

d. Determines which sugars an organism can ferment.

Explanation:

Phenol red glucose, lactose, and sucrose fermentation tests are valuable because,

a. Helps distinguish species of bacteria that are different, but look the same under the microscope

This is a right choice as this test is typically used to differentiate Gram negative enteric bacteria which are mostly Gram negative rods and look the same under the microscope.

b. Characterize metabolic strategies of newly discovered bacteria

Phenol red fermentation tests uses three sugars namely glucose, lactose and sucrose in each broth. It mainly tests an organism's ability to ferment a particular sugar. It cannot describe the metabolic pathways of a new strain of bacteria. Hence this choice does not apply.

c. These fermentation tests can identify an organism with no other information

This choice does not apply as several fermentation tests are also available that has to be done to identify an organism with no other information. Phenol red fermentation test is one of the fermentation tests to detect an organism.

d. Determines which sugars an organism can ferment

The difference in fermentation pattern of several sugars can be useful for differentiating organisms among species of bacteria. Hence this choice is correct.