Microbiology Lab Exercise 9: Phenylalanine Deaminase and Nitrate Reductase

Phenylalanine Deaminase

The name of the enzyme that removes the amino group from phenylalanine to produce phenylpyruvic acid and ammonia.

Phenylpyruvic acid and ammonia

What are the products of deamination of phenylalanine?

Ferric Chloride

What compound is used to test for the presence of phenylpyruvic acid

Green

What color will the ferric chloride- phenylpyruvic acid be?

Proteus, Providencia, and Morganella

What genera contain phenylalanine deaminase?

Deamination

The process of removing an amino group from a compound

Aerobic Respiration

When organisms use an electron transport chain to generate a proton gradient to power oxidative phosphorylation of ATP and the final electron acceptor is oxygen.

Anaerobic respiration

When organisms including facultative anaerobes use an ETC and proton gradient to make ATP but use other final electron acceptors like nitrate.

Denitrification

A process where organisms reduce nitrate to nitrite to nitric oxide, to nitrous oxide to dinitrogen gas.

Nitrate/Nitrite Ammonification

Organisms that reduce nitrite to ammonium.

Nitrate Reductase

If gas is present in the Durham tube of the nitrate broth tube then we know that the ___________ __________ enzyme was present.

Nitrate Reagent A and Nitrate Reagent B

What are the reagents added to the tube of nitrate broth to see if a reaction occured?

Red Diazo Dye

NRA and NRB will react with nitrate to form what product?

Do not

If you add zinc powder to the bacteria with NFA and NFB and it forms the red dye if the bacteria __________ have the enzyme.

Do

If you add zinc powder to the bacteria with NFA and NFB and it does not form the red dye then bacteria __________ have the enzyme.

Zinc

__________ reduces Nitrate to Nitrite so it can be used to test for the presence of the substrate nitric oxide.

Denitrification

If gas is detected in the Durham tubes then we know that ___________ occured and after nitrate was reduced to nitrite it was further broken down into gases like NO, N2O, and N2.

Production

A __________ of products can indicate that a reaction occurred. For example, detecting NO2 (red color appears) with Nitrate Reagent A and Nitrate Reagent B.

Absence

The ___________ of substrates can also indicate that a reaction occurred. For example, Zn fails to reduce NO3 and cause the reddish appearance that occurs when exposed to NRA and NRB.

Nitrate Reductase

If a red color change is only detected after zinc is added then the bacteria does not contain ______ _____

Yes

The tube with Morganella morganii bacteria that grew on a medium with phenylalanine produced a dark green compound when ferric chloride was added. Do they have Phenylalanine Deaminase?

Phenylalanine Deaminase

The tube with Proteus Vulgaris bacteria that grew on a medium with phenylalanine produced a dark green compound when ferric chloride was added. Which enzyme do they have that allows for this reaction?

No

The bacteria Acinetobacter lwoffii grew on a medium with phenylalanine. When ferric chloride was added there was no change in color. Does this bacteria have phenyalanine deaminase?

No

The bacteria Escherichia coli does not have phenylalanine deaminase. If grown on a medium with phenylalanine then treated with ferric chloride will there be a green compound?

No

When Pseudomonas aeruginosa was grown on a medium with phenylalanine and had ferric chloride added. No change in color occurred. Does this bacterium have the enzyme phenylalanine deaminase?

No

The bacteria Acinetobacter lwoffii was grown in a NO3 broth. When reagents NRA and NRB were added no change in color occured. When zinc was added the broth turned red. Do these bacteria have nitrate reductase?

Yes

The bacteria Escherichia coli was grown in a NO3 broth. When reagents NRA and NRB were added a change in color to red occurred. Do these bacteria have nitrate reductase?

Culture turns red

The bacteria Morganella morganii contains the enzyme nitrate reductase. When grown in a NO3 broth then treated with NRA and NRB what will occur.

Nitrite

When Proteus vulgaris was grown in NO3 broth then treated with NRA and NRB it turned red. What compound reacted with NRA and NRA to create the red diazo dye? (Hint: created through reaction catalyzed by nitrate reductase)

Yes

The bacteria Pseudomonas aeruginosa did not turn red after the addition of NRA/NRB or the addition of zinc. Does these bacteria contain nitrate reductase?

Denitrification occurs and Nitrite was converted to gaseous nitrogen compounds like NO, N2O, and N2

The bacteria Pseudomonas aeruginosa did not turn red after the addition of NRA/NRB or the addition of zinc and gas was produced in the Durham tube. If nitrate was converted to nitrite why did the broth not turn red?

Gas

The bacteria Pseudomonas aeruginosa does contain nitrate reductase but also performs denitrification. What will be produced by these reactions?