Oxygen tolerance and toxicity Flashcards

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1
Q

What is an oxic/aerobic environment?

A

An environment that contains any amount of O2

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2
Q

What is an anoxic/anaerobic environment?

A

No O2 in the environment whatsoever

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3
Q

What is an aerobe?

A

An organism that can use O2 as TEA in aerobic respiration

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4
Q

What is an obligate aerobe?

A

An organism that can only do aerobic respiration and nothing else, so requires O2 at all time

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5
Q

How common are obligate aerobes? Where are they found?

A

Relatively rare. Having no backup isn’t the best plan. They’re found in areas where the oxygen source is constantly replenished, like our upper respiratory tract

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6
Q

How do you culture obligate aerobes?

A

The culture needs to be constantly shaken or aerated

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7
Q

What are facultative anaerobes?

A

Organisms that can use and tolerate oxygen, and will preferentially use it if its there. But they switch to another pathway if its not there and do perfectly fine without it

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8
Q

Where how common are facultative anaerobes? Where are they found?

A

Super common, found just about everywhere

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9
Q

How do you culture facultative anaerobes?

A

However you want

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10
Q

What are microaerophiles?

A

Organisms that require O2 for metabolism, but only very small amounts because they have enzymes that get destroyed by O2

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11
Q

Where how common are microaerophiles? Where are they found?

A

Pretty rare, can only live in a very narrow range of O2 concentrations. Found in our stomachs

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12
Q

How do you culture microaerophiles?

A

Candle jar

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13
Q

What is an anaerobe?

A

An organism that lacks the machinery needed to use aerobic respiration

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14
Q

What are aerotolerant anaerobes?

A

Organisms that only use fermentation and don’t care if O2 is there or not

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15
Q

What are obligate anaerobes?

A

Organisms that are poisoned by O2 and must live in an oxygen free environment

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16
Q

Where how common are obligate anaerobes? Where are they found?

A

Surprisingly common. Found in places like our colons and in the centre of biofilms

17
Q

How do you culture obligate anaerobes?

A

Have to be in a special cabinet with no oxygen. Hard to culture

18
Q

How do you test for oxygen tolerance?

A

Grow the bacteria in a liquid culture without mixing and look where the growth is

19
Q

Where does an obligate aerobe grow in an unmixed liquid culture tube?

A

Only at the top

20
Q

Where does a facultative anaerobe grow in an unmixed liquid culture tube?

A

Everywhere, but especially dense at the top

21
Q

Where does an obligate anaerobe grow in an unmixed liquid culture tube?

A

Only at the bottom

22
Q

Where does an aerotolerant anaerobe grow in an unmixed liquid culture tube?

A

Everywhere equally

23
Q

Where does a microaerophile grow in an unmixed liquid culture tube?

A

Right below the oxic zone

24
Q

How can oxygen be dangerous to cells?

A

ROS are byproducts of aerobic metabolism

25
Q

What are 3 ROS that need to be dealt with?

A

Superoxide, hydrogen peroxide, hydroxyl radicals

26
Q

How do macrophages use ROS to kill bacteria?

A

They engulf bacteria and put them in a phagosome. The phagosome fuses with a lysosome, then reactions take place in the phagosome that create ROS to kill the bacteria

27
Q

How do bacteria detoxify ROS?

A

Aerobes and aerotolerant bacteria produce enzymes that will detoxify ROS

28
Q

What are the 3 enzymes that detoxify ROS?

A

Superoxide dimutase, catalase, peroxidase

29
Q

What does superoxide dimutase do?

A

Converts superoxides to O2 and H2O2

30
Q

Is superoxide dimutase found in all aerobes?

A

Yes

31
Q

What are the two enzymes that detoxify hydrogen peroxide?

A

Catalase and peroxidase

32
Q

What does catalase do?

A

Converts H2O2 to O2 and H2O

33
Q

Is catalase found in all aerobes?

A

No, only found in some

34
Q

What does peroxidase do?

A

Converts H2O2 and NADH to water and NAD+

35
Q

How do you tell if a bacteria has catalase or peroxidase?

A

Catalase test. You place a drop of H2O2 on the bacteria and look for bubbles. If they do bubble, they have catalase. If they don’t they have peroxidase

36
Q

Is there an enzyme to get rid of hydroxyl radicals?

A

No. If the other enzymes are working hydroxyl radicals will never be produced