Lecture 15 - Chemolithotrophy

Question 1

chemolithotrophy

Answer 1

involves the generation of energy from the oxidation of inorganic chemicals (from electron donors)

Question 2

Most chemolithotroph are _____ (obtain carbon from _____ )

Answer 2

autotrophs, CO2

Question 3

mixotrophs

Answer 3

chemolithotrophstlat have an inorganic energy source, but organic carbon source

Question 4

What are 4 examples of inorganic electron donors?

Answer 4

1. hydrogen
2. reduced sulfur compounds
3. ferrous irron
4. ammonia and nirtate

Question 5

• H2S
• So
• S2O3 2- (throsulfate)
  SO4 2- is generally the end product.

Answer 5

electron donors used by colorless sulfur bacteria

Question 6

• nitrate (NO3-)
• sulfate (SO4 2-)
• ferric iron (Fe 3+)
• CO2
• halogenated chemicals (e.g. vinyl chloride)

Answer 6

anaerobic oxidation of hydrogen

Question 7

oxygen is the electron acceptor, oxygen is reduced to water

[1 of 2 pathways for oxidation of reduced sulfur compounds]

Answer 7

aerobic oxidation of hydrogen

Question 8

Biochemistry of aerobic H2 oxidation the reaction is catalyzed by the enzyme _____.

Answer 8

hydrogenase

Question 9

1. The most common pathway uses the enzyme _____ _____.

[1 of 2 pathways for oxidation of reduced sulfur compounds/sulfite oxidation]

Answer 9

sulfite oxidase

Question 10

2. another uses the enzyme _____ _____ (APS) reductase. APS is also found in sulfate reducing bacteria.

[1 of 2 pathways for oxidation of reduced sulfur compounds/sulfite oxidation]

Answer 10

adenosine phosphosulfate (APS) reductase

Question 11

Both pathways for sulfite oxidation produce what?

[pathways for oxidation of reduced sulfur compounds/sulfite oxidation]

Answer 11

sulfate, SO4 2-

Question 12

Why are some oxidizers (e.g. ferrous iron oxidizers) called acidophilic?

Answer 12

because of stability of ferrous iron under different conditions

• ferrous iron is oxidizes non-biologically to ferric iron (ferrous iron is no longer available as an electron donor) in oxic (nuetral PH) conditions
• ferrous iron is stable in anoxic (acidic PH) conditions

Question 13

Summarize the acid min drainage problem.

Answer 13

Iron oxidizers are key microorganisms in the acid min drainage problem.

Coal mining exposes pyrite (FeS2) to oxygen

A set of reactions occur resulting in the creation of acidic conditions.

Question 14

1. Indicator reaction

[acid mine drainage problem]

Answer 14

pyrite (FeS2) is exposed to oxygen

chemical oxidation of pyrite producing

• sulfate SO4 2-
• ferrous iron Fe 2+
• protons (acidic conditions)

Question 15

2. propagation cycle

[acid mine drainage problem]

Answer 15

iron oxidizing microorganisms oxidize
Fe 2+ —> Fe 3+

ferric iron can the react spontaneously with more pyrite
So4 2-, Fe 2+, protons

Question 16

3. cycle repeats

[acid mine drainage problem]

Answer 16

pyrite is spontaneously oxidized and acidic conditions

Question 17

• acidic conditions are inherently bad for ecosystems

additional impacts:
dissolved toxic metals e.g. aluminum

Answer 17

consequences of acid mine drainage

Question 18

1. ammonia oxidation

[Step 1 of 2 process of nitrification]

Answer 18

I) ammonia monooxygenase (AMO)
oxidizes ammonia producing hydroxylamine (NH2OH)

II) hydroxylamine oxireductase (HAO)
oxidizes hydroxylamine producing nitrite (NO2 -)

Question 19

nitrification

Answer 19

the microbial conversion of ammonia (NH3) to nitrate (NO3-)

Question 20

typically have genus names that start with “nitroso”

e.g. nitrosomona, nitrosococcus

Answer 20

ammonia oxidizing bacteria

Question 21

2. nitrite oxidation

[Step 1 of 2 process of nitrification]

Answer 21

involves the enzyme nitrate oxyredutase (NOR) oxidizes nitrous (NO2 -) producing nitrate (NO3 -)

Question 22

typically have genus names that start with “nitro”

e.g. nitrospira

Answer 22

nitrite oxidizing bacteria

Question 23

ANAMOX stands for …

Answer 23

anoxic ammonia oxidation

Question 24

What is ANAMOX?

Answer 24

anoxic ammonia oxidation; oxidation of ammonia with nitrate as the electron acceptor yielding nitrogen gas

Question 25

ANAMOX bacteria grows a) rapidly or b) slowly.

Answer 25

b) slowly