Lab 17 - Biotyping: O2 tolerance

Question 1

what does “redox” stand for?

Answer 1

reduction-oxidation

Question 2

in the electron transport chain, NADH and FADH dump electrons on oxygen to form water. What type of reaction is this?

Answer 2

Oxygen is REDUCED to water

Question 3

define oxidation

Answer 3

loss of electrons

Question 4

define reduction

Answer 4

gain of electrons

Question 5

what is the pneumonic for redox reactions?

Answer 5

OIL RIG

Question 6

what does ROS stand for? what does it mean?

Answer 6

Reactive oxygen species.
In cells, oxygen can also be reduced to other products called reactive oxygen species (ROS). These are toxic.

Question 7

why are ROS toxic?

Answer 7

because they oxidize (strip electrons from) and inactivate biomolecules. this may lead to cell death

Question 8

why are detoxification enzymes produced by the cells?

Answer 8

to get rid of ROS

Question 9

what are the two detoxification enzymes?

Answer 9

superoxide dismutase and catalase

Question 10

what does superoxide dismutase do?

Answer 10

detoxifies superoxide radical

Question 11

what does catalase do?

Answer 11

detoxifies hydrogen peroxide

Question 12

What chemical formula is superoxide dismutase a part of?

Answer 12

2H+ + 2O2 —–superoxide dismutase——> H202 +O2

Question 13

What chemical formula is catalase a part of?

Answer 13

2H2O2 —-catalase—-> 2H20 + O2

Question 14

what is the catalase test?

Answer 14

used to identify organisms that produce the enzyme catalase

Question 15

what is a positive catalase test?

Answer 15

bubbles formed, indicating the production of oxygen

Question 16

what is the thioglycolate broth used to do?

Answer 16

to determine the oxygen requirements of microorganisms.

Question 17

what are the nutrients in a thioglycolate broth?

Answer 17

yeast extract and a casein protein to digest

Question 18

what are the reducing agents in a thioglycolate broth? what does this mean?

Answer 18

They are sodium thioglycolate and cystine.
They reduce O2 to H2O

Question 19

what percentage of agar is in a thioglycolate broth? what does this do?

Answer 19

A low percentage, 0.75%.
This minimizes O2 diffusion into the tube

Question 20

what is the O2 indicator on the thioglycolate broth? what color is it when oxidized? reduced?

Answer 20

resazurin, which is pink when oxidized and clear when reduced

Question 21

where does O2 diffusion happen in a thioglycolate broth?

Answer 21

only at the top of the tube

Question 22

in a thioglycolate tube, if there is growth only at the top of the tube, what type of organism is it?

Answer 22

Obligate aerobe

Question 23

in a thioglycolate tube, if there is growth only at the bottom of the tube, what type of organism is it?

Answer 23

Obligate anaerobe

Question 24

in a thioglycolate tube, if there is more growth at the top of the tube, and less as it goes down, what type of organism is it?

Answer 24

Facultative anaerobe

Question 25

in a thioglycolate tube, if there is growth evenly all over the tube, what type of organism is it?

Answer 25

aerotolerant anaerobe

Question 26

in a thioglycolate tube, if there is growth a little below the top of the tube, what type of organism is it?

Answer 26

microaerophiles

Question 27

what is an anaerobic jar?

Answer 27

It is a gas generator envelope, chemicals in the sachet react with O2 to produce CO2 and H2O. It prevents oxygen from coming in.

Question 28

what does the indicator strip do?

Answer 28

It is methylene blue and becomes blue when oxidized and clear when reduced

Question 29

P. aeruginosa: -Thioglycolate tube: -Plate WITH O2: -Plate WITHOUT O2: -Catalase:

Answer 29

-Thioglycolate tube: obligate aerobe -Plate WITH O2: growth -Plate WITHOUT O2: no growth -Catalase: positive

Question 30

E. coli: -Thioglycolate tube: -Plate WITH O2: -Plate WITHOUT O2: -Catalase:

Answer 30

-Thioglycolate tube: facultative anaerobe -Plate WITH O2: growth -Plate WITHOUT O2: growth -Catalase: positive

Question 31

E. faecalis: -Thioglycolate tube: -Plate WITH O2: -Plate WITHOUT O2: -Catalase:

Answer 31

-Thioglycolate tube: aerotolerant anaerobe -Plate WITH O2: growth -Plate WITHOUT O2: growth -Catalase: negative

Question 32

C. sporogenes: -Thioglycolate tube: -Plate WITH O2: -Plate WITHOUT O2: -Catalase:

Answer 32

-Thioglycolate tube: obligate anaerobe -Plate WITH O2: no growth -Plate WITHOUT O2: growth -Catalase: negative

Question 33

usually, will a facultative anaerobe have a positive or negative catalase result?

Answer 33

positive

Question 34

usually, will an aerotolerant anaerobe have a positive or negative catalase result?

Answer 34

negative