Flashcards in MIDTERM 2 NITRATE REDUCTION Deck (19)
What does denitrification result in?
the conversion of nitrate to nitrite to Dinitrogen gas, which is released into the atmosphere
Qualities of denitrifying bacteria?
1. either obligate aerobes
2. facultative organisms that grow most rapidly in presence of oxygen
in what 2 ways does the presence of oxygen serve to reduce the amount of denitrification
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.
What does amount of oxygen in soil depend on?
1. degree of aeration
2. moisture content of the soil
What are we testing in the nitrate test?
We will test the ability of pure cultures to reduce nitrate either partially to nitrite or completely to dinitrogen.
What are we looking for in the nitrate test?
We will be testing for the presence or absence of nitrite which is the intermediate product
What does the nitrate broth consist of?
1. Beef extract
3. potassium nitrate
What two reagents are used to test for nitrite after incubation in nitrate broth?
What is Reagent A
What is Reagent B
What happens to the reagent A and B in presence of nitrite?
The reagents causes the culture to turn red.
What does detection of nitrite mean?
it means your organism is able to reduce nitrate
What happens if theres no color change after adding in Reagent A and B?
1. Your organism might have gone through a complete reduction from nitrate--> Dinitrogen or
2. Your organism has no nitrate reduction
What do you add to the culture if it doesnt change colors after Reagent A and B are added?
you add zinc dust
What does adding Zinc Dust do to the culture?
it reduces nitrate to nitrite, which then reacts with the reagents already present to produce a red color
What is Nitratase and its significance?
it allows the use of the oxygen in nitrate as hydrogen acceptor, converting nitrate to nitrite. Niratase is the enzyme that controls this.
What prevents nitrate reduction?
presence of free oxygen
How do multiplying organisms deal with the free oxygen that prevents nitrate reduction?
they use up the oxygen first and then utilize nitrate.