MIDTERM 2 Oxygen Requirements

Question 1

Special quality of facultative bacteria?

Answer 1

they have enzyme systems enabling them to utilize free oxygen or some alternative oxygen source, such as nitrate. they may prefer either an aerobic or anaerobic lifestyle or have no preference at all.

Question 2

What test is used for oxygen requirements?

Answer 2

Thioglycolate medium

Question 3

What is the significance of the thioglycolate medium?

Answer 3

used to determine the oxygen requirements for an organism

Question 4

What is contained in the Thioglycolate medium?

Answer 4

1. Glucose
2. Cystine
3. sodium thioglycolate
4. Resazurin (dye)

Question 5

Why is Thioglycolate used?

Answer 5

its a reducing agent that lowers its oxidation-reduction potential.

Question 6

What is Resazurin and why is it used?

Answer 6

its a dye and its used to indicate presence of oxygen

Question 7

What color does the dye turn into under presence of oxygen?

Answer 7

Pink

Question 8

When inoculating our medium, why is it important to do it gently?

Answer 8

because it can shake and this causes more oxygen to be taken into the medium

Question 9

How long do we incubate the thioglycolate tubes for?

Answer 9

48 Hours

Question 10

Why is it important to check the thioglyoclate tubes at 24 hours?

Answer 10

Because as the culture becomes denser, particularly at the top of the tube, the cells may clump together and sink from the bottom, giving the false appearance of no growth in the top layer.