Lab 17 - Biotyping: O2 tolerance Flashcards
what does “redox” stand for?
reduction-oxidation
in the electron transport chain, NADH and FADH dump electrons on oxygen to form water. What type of reaction is this?
Oxygen is REDUCED to water
define oxidation
loss of electrons
define reduction
gain of electrons
what is the pneumonic for redox reactions?
OIL RIG
what does ROS stand for? what does it mean?
Reactive oxygen species.
In cells, oxygen can also be reduced to other products called reactive oxygen species (ROS). These are toxic.
why are ROS toxic?
because they oxidize (strip electrons from) and inactivate biomolecules. this may lead to cell death
why are detoxification enzymes produced by the cells?
to get rid of ROS
what are the two detoxification enzymes?
superoxide dismutase and catalase
what does superoxide dismutase do?
detoxifies superoxide radical
what does catalase do?
detoxifies hydrogen peroxide
What chemical formula is superoxide dismutase a part of?
2H+ + 2O2 —–superoxide dismutase——> H202 +O2
What chemical formula is catalase a part of?
2H2O2 —-catalase—-> 2H20 + O2
what is the catalase test?
used to identify organisms that produce the enzyme catalase
what is a positive catalase test?
bubbles formed, indicating the production of oxygen
what is the thioglycolate broth used to do?
to determine the oxygen requirements of microorganisms.
what are the nutrients in a thioglycolate broth?
yeast extract and a casein protein to digest
what are the reducing agents in a thioglycolate broth? what does this mean?
They are sodium thioglycolate and cystine.
They reduce O2 to H2O
what percentage of agar is in a thioglycolate broth? what does this do?
A low percentage, 0.75%.
This minimizes O2 diffusion into the tube
what is the O2 indicator on the thioglycolate broth? what color is it when oxidized? reduced?
resazurin, which is pink when oxidized and clear when reduced
where does O2 diffusion happen in a thioglycolate broth?
only at the top of the tube
in a thioglycolate tube, if there is growth only at the top of the tube, what type of organism is it?
Obligate aerobe
in a thioglycolate tube, if there is growth only at the bottom of the tube, what type of organism is it?
Obligate anaerobe
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?
Facultative anaerobe
in a thioglycolate tube, if there is growth evenly all over the tube, what type of organism is it?
aerotolerant anaerobe
in a thioglycolate tube, if there is growth a little below the top of the tube, what type of organism is it?
microaerophiles
what is an anaerobic jar?
It is a gas generator envelope, chemicals in the sachet react with O2 to produce CO2 and H2O.
It prevents oxygen from coming in.
what does the indicator strip do?
It is methylene blue and becomes blue when oxidized and clear when reduced
P. aeruginosa:
-Thioglycolate tube:
-Plate WITH O2:
-Plate WITHOUT O2:
-Catalase:
-Thioglycolate tube: obligate aerobe
-Plate WITH O2: growth
-Plate WITHOUT O2: no growth
-Catalase: positive
E. coli:
-Thioglycolate tube:
-Plate WITH O2:
-Plate WITHOUT O2:
-Catalase:
-Thioglycolate tube: facultative anaerobe
-Plate WITH O2: growth
-Plate WITHOUT O2: growth
-Catalase: positive
E. faecalis:
-Thioglycolate tube:
-Plate WITH O2:
-Plate WITHOUT O2:
-Catalase:
-Thioglycolate tube: aerotolerant anaerobe
-Plate WITH O2: growth
-Plate WITHOUT O2: growth
-Catalase: negative
C. sporogenes:
-Thioglycolate tube:
-Plate WITH O2:
-Plate WITHOUT O2:
-Catalase:
-Thioglycolate tube: obligate anaerobe
-Plate WITH O2: no growth
-Plate WITHOUT O2: growth
-Catalase: negative
usually, will a facultative anaerobe have a positive or negative catalase result?
positive
usually, will an aerotolerant anaerobe have a positive or negative catalase result?
negative
