Practical 2 Study Guide (Carbs and Nitrate)

What does carbohydrate fermentation test for?

the ability of an organism to ferment different carbs into acid and liberate gas

What is the Durham tube apparatus?

a tube containing phenol red broth, the test carbohydrate, phenol red pH indicator, and the Durham tube

What is the small tube within the Durham tube apparatus?

the Durham tube

What pH indicator is in the Durham tube apparatus?

a phenol red pH indicator

What broth is in the Durham tube apparatus?

Phenol red broth

What happens in the Durham tube apparatus if acid is produced?

the phenol red turns yellow

What happens in the Durham tube apparatus if gas is produced?

a bubble will appear in the Durham tube

What does nitrate reduction test for?

the ability of an organism to reduce nitrate into nitrite or further into ammonia or nitrogen gas

What is the chemical symbol for nitrate?

NO3-

What is the chemical symbol for nitrite?

NO2-

What is the medium for nitrate reduction?

tryptic nitrate broth which contains nitrate

What do you do after inoculating tryptic nitrate broth?

add sulfanilic acid and alpha napthylamine

What are the reagent tests for nitrite?

sulfanilic acid and alpha napthylamine

What happens in tryptic nitrate if the tube turns blood red after adding the reagents?

the organism only has the nitrate reductase enzyme

What do you do with tryptic nitrate if no color change occurs after adding the reagents?

add powdered zinc metal

What does powdered zinc metal do with tryptic nitrate?

it chemically changes the nitrate to nitrite

What happens if the tube of tryptic nitrate turns pink or red after the zinc is added?

the microorganism had no enzymes for the pathway

What does it mean if there is no color change to the tryptic nitrate after zinc is added?

the organism has both nitrate reductase and nitrite reductase

What happens to the nitrate if the organism has the nitrate reductase enzyme?

the nitrate is converted into either ammonia or nitrogen gas