MIDTERM 2 NITRATE REDUCTION

Question 1

What does denitrification result in?

Answer 1

the conversion of nitrate to nitrite to Dinitrogen gas, which is released into the atmosphere

Question 2

Qualities of denitrifying bacteria?

Answer 2

1. either obligate aerobes

2. facultative organisms that grow most rapidly in presence of oxygen

Question 3

in what 2 ways does the presence of oxygen serve to reduce the amount of denitrification

Answer 3

1. provides the bacteria with an alternative terminal electron acceptor and therefore protects the nitrate against use for this purpose thus reducing nitrate loss
2. Good oxygen levels promote the growth and function of aerobic nitrifying bacteria, increasing the production of nitrate from ammonia.

Question 4

What does amount of oxygen in soil depend on?

Answer 4

1. degree of aeration

2. moisture content of the soil

Question 5

What are we testing in the nitrate test?

Answer 5

We will test the ability of pure cultures to reduce nitrate either partially to nitrite or completely to dinitrogen.

Question 6

What are we looking for in the nitrate test?

Answer 6

We will be testing for the presence or absence of nitrite which is the intermediate product

Question 7

What does the nitrate broth consist of?

Answer 7

1. Beef extract
2. peptone
3. potassium nitrate

Question 8

What two reagents are used to test for nitrite after incubation in nitrate broth?

Answer 8

Reagent A

Reagent B

Question 9

What is Reagent A

Answer 9

Sulfanilic acid

Question 10

What is Reagent B

Answer 10

DMAP

Question 11

What happens to the reagent A and B in presence of nitrite?

Answer 11

The reagents causes the culture to turn red.

Question 12

What does detection of nitrite mean?

Answer 12

it means your organism is able to reduce nitrate

Question 13

What happens if theres no color change after adding in Reagent A and B?

Answer 13

it means

1. Your organism might have gone through a complete reduction from nitrate–> Dinitrogen or
2. Your organism has no nitrate reduction

Question 14

What do you add to the culture if it doesnt change colors after Reagent A and B are added?

Answer 14

you add zinc dust

Question 15

What does adding Zinc Dust do to the culture?

Answer 15

it reduces nitrate to nitrite, which then reacts with the reagents already present to produce a red color

Question 16

What is Nitratase and its significance?

Answer 16

it allows the use of the oxygen in nitrate as hydrogen acceptor, converting nitrate to nitrite. Niratase is the enzyme that controls this.

Question 17

What prevents nitrate reduction?

Answer 17

presence of free oxygen

Question 18

How do multiplying organisms deal with the free oxygen that prevents nitrate reduction?

Answer 18

they use up the oxygen first and then utilize nitrate.

Question 19

Why is it bad to use too much zinc dust?

Answer 19

it could not only reduce nitrate to nitrite, but also further reduce the nitrite to N2