Lecture 18 - Iron-Sulfur Cycling Flashcards Preview

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Flashcards in Lecture 18 - Iron-Sulfur Cycling Deck (49)
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1

How is sulfur oxide emitted into the atmosphere?

microbial processes | fossil fuel burning | volcanoes and host springs

2

What is the largest reservoir of sulfur on the planet? What form is sulfur in within this reservoir? Is it actively cycled?

ocean | sulfate | yes

3

Which sulfur reservoir is not actively cycled?

Earth's crust

4

What form is sulfur in within the atmospheric sulfur reservoir?

sulfur oxide and hydrogen sulfide

5

What are the 4 processes of the sulfur cycle?

sulfur assimilation | sulfur mineralization | sulfur oxidation | sulfur reduction

6

What is sulfur assimilation?

taking sulfate (SO4) and incorporating it into biological molecules | requires 2 ATP

7

What is the predominant form of sulfur in the environment?

sulfate (SO4)

8

What kind of reaction (reduction or oxidation) does sulfur assimilation occur within the cell?

reduction reaction

9

What does "-SH" stand for?

organic sulfur

10

What is sulfur mineralization?

a metabolic reaction, opposite of assimilation process | releasing sulfur from organic molecules | anaerobic and aerobic environment

11

What do the process of sulfur assimilation and mineralization cycle sulfur between, since they are opposites?

organic and inorganic forms of sulfur

12

What is H2S?

hydrogen sulfide = toxic gas

13

What is sulfur oxidation?

H2S >>> SO4 via oxidation reactions

14

What are the 2 ways sulfur is oxidized in sulfur oxidation? (aerobically)

H2S >>> So (elemental sulfur) | So >>> SO4 (results in acid)

15

Which step in sulfur oxidation results in acid mine drainage and why?

So >>> SO4 because it's really So + H2O >>> SO4 + 2H+ and that mixed together results in sulfuric acid

16

How does the So >>> SO4 reaction cause acid mine drainage? What is acid mine drainage useful in?

in low pH = causes metals to precipitate out | useful in metal recovery

17

What is a way that sulfur is oxidized anaerobically?

use NO3 as e- acceptor = end up producing calcium sulfate (gypsum)

18

What is photoautotrophic sulfur oxidation?

photoautotrophic organisms that can oxidize sulfur by using light energy

19

Which organisms are capable of photoautotrophic sulfur oxidation?

green and purple sulfur bacteria

20

Why are the green and purple sulfur bacteria an important group of organisms?

they remove sulfide from the environment and oxidize it to sulfur | H2S >>> So

21

What is sulfur reduction?

inhibited by oxygen | makes H2S = can cause metal corrosion

22

What are the 3 ways sulfur is reduced?

sulfur assimilation | sulfur respiration | dissimilation

23

What is sulfur respiration?

So >>> H2S | uses acetate as one of the reactants

24

What is sulfur dissimilation?

SO4 >>> H2S | uses methanol as one of the reactants

25

In sulfur reduction, where do methanol and acetate come from? What does it mean?

carbon cycle from fermenter microbes | an anaerobic interaction between the sulfur reducing bacteria and the carbon-fermenting bacteria and methanogens

26

What are 5 things sulfur is required for?

cysteine | methionine | vitamins | hormones | co-enzymes

27

What can the sulfur cycle form in the environment?

acid rain | acid mine drainage | metal corrosion

28

Even though iron is highly abundant in the Earth's crust, why is it not readily used?

bioavailability is limited = not in the form cells can use it

29

Why is iron important? What is it used for?

all cells need iron - used as co-factors in respiration and photosynthesis

30

If all cells need iron, how do microbes attain it when the bioavailability of iron is limited?

cells have developed different ways of attaining iron