Lecture 15 - Chemolithotrophy Flashcards
chemolithotrophy
involves the generation of energy from the oxidation of inorganic chemicals (from electron donors)
Most chemolithotroph are _____ (obtain carbon from _____ )
autotrophs, CO2
mixotrophs
chemolithotrophstlat have an inorganic energy source, but organic carbon source
What are 4 examples of inorganic electron donors?
- hydrogen
- reduced sulfur compounds
- ferrous irron
- ammonia and nirtate
- H2S
- So
- S2O3 2- (throsulfate)
SO4 2- is generally the end product.
electron donors used by colorless sulfur bacteria
- nitrate (NO3-)
- sulfate (SO4 2-)
- ferric iron (Fe 3+)
- CO2
- halogenated chemicals (e.g. vinyl chloride)
anaerobic oxidation of hydrogen
oxygen is the electron acceptor, oxygen is reduced to water
[1 of 2 pathways for oxidation of reduced sulfur compounds]
aerobic oxidation of hydrogen
Biochemistry of aerobic H2 oxidation the reaction is catalyzed by the enzyme _____.
hydrogenase
- The most common pathway uses the enzyme _____ _____.
[1 of 2 pathways for oxidation of reduced sulfur compounds/sulfite oxidation]
sulfite oxidase
- 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]
adenosine phosphosulfate (APS) reductase
Both pathways for sulfite oxidation produce what?
[pathways for oxidation of reduced sulfur compounds/sulfite oxidation]
sulfate, SO4 2-
Why are some oxidizers (e.g. ferrous iron oxidizers) called acidophilic?
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
Summarize the acid min drainage problem.
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.
- Indicator reaction
[acid mine drainage problem]
pyrite (FeS2) is exposed to oxygen
chemical oxidation of pyrite producing
- sulfate SO4 2-
- ferrous iron Fe 2+
- protons (acidic conditions)
- propagation cycle
[acid mine drainage problem]
iron oxidizing microorganisms oxidize
Fe 2+ —> Fe 3+
ferric iron can the react spontaneously with more pyrite
So4 2-, Fe 2+, protons
- cycle repeats
[acid mine drainage problem]
pyrite is spontaneously oxidized and acidic conditions
- acidic conditions are inherently bad for ecosystems
additional impacts:
dissolved toxic metals e.g. aluminum
consequences of acid mine drainage
- ammonia oxidation
[Step 1 of 2 process of nitrification]
I) ammonia monooxygenase (AMO)
oxidizes ammonia producing hydroxylamine (NH2OH)
II) hydroxylamine oxireductase (HAO)
oxidizes hydroxylamine producing nitrite (NO2 -)
nitrification
the microbial conversion of ammonia (NH3) to nitrate (NO3-)
typically have genus names that start with “nitroso”
e.g. nitrosomona, nitrosococcus
ammonia oxidizing bacteria
- nitrite oxidation
[Step 1 of 2 process of nitrification]
involves the enzyme nitrate oxyredutase (NOR) oxidizes nitrous (NO2 -) producing nitrate (NO3 -)
typically have genus names that start with “nitro”
e.g. nitrospira
nitrite oxidizing bacteria
ANAMOX stands for …
anoxic ammonia oxidation
What is ANAMOX?
anoxic ammonia oxidation; oxidation of ammonia with nitrate as the electron acceptor yielding nitrogen gas
ANAMOX bacteria grows a) rapidly or b) slowly.
b) slowly
